miJBENHAUS:; ■vy■•;■•■:.d^^<':>^^f<^*y^: ^^^»1 CROPS tOL . 'H.P. Class. Book. Tf T3 GopyiigMI^^ C.OPVRICHT DEPOSm DISEASES OF TRUCK CROPS AND THEIR CONTROL OTHER WORKS BY THE SAME AUTHOR The Culture and Diseases of the Sweet Pea - $2.00 net. Profusely Illustrated Diseases of Greenhouse Plants (In Preparation) Diseases of the Sweet Potato (In Preparation) E. P. DUTTON & COMPANY NEW YORK DISEASES OF TRUCK CROPS AND THEIR CONTROL BY J. J. TAUBENHAUS, Ph.D. Plant Pathologist and Physiologist to the Agricultural and Mechanical College of Texas Author of " Culture and Diseases of the Sweet Pea " • NEW YORK E. P. DUTTON & COMPANY 681 FIFTH AVENUE Copyright, 191 8 By E. P. DUTTON & COMPANY M 2b (9i8 PRINTED IN THE UNITBD STATES OF AMERICA S'C:.A437934 TO MY FRIEND B. KACZER PREFACE The world never has faced a greater shortage of food than to-day. War's destructive agencies have added themselves to our old invisible foes, namely parasitic and disease-producing bacteria and fungi. More than half of our diet is made up of vege- tables. They furnish the necessary food bulk which the body requires, supply important nutritive ele- ments, and act as stimulants to a better blood circu- lation. According to the Thirteenth Census of the United States the area devoted to truck crops in the United States in 1909 was estimated at 7,436,551 acres. The total money value of the truck crops grown on this acreage was estimated at $301,104,144. The crops thus estimated included asparagus, ;beans (green), beans (dry), beets, cabbage, cauliflower, corn (pop and sweet), cantaloups, carrots, celery, chicory, cucumbers, egg plant, horse-radish, kale, lettuce, mint, okra, onions, parsley, parsnip, peas (green), peas (dry), peppers, pumpkin, radish, rhubarb, rutabagas, spinach, sprouts, squash, sun- flower, sweet potato and yam, tomatoes, turnips, and watermelon. We scarcely realize the large sums of money which the trucker loses annually from specific plant dis- eases, because there are few available data as to vii viii Preface the money losses. But as an example, the following figures, kindly given to the writer by Professor R. P. Haskell, Pathological Inspector of the United States Department of Agriculture, will be of compelling interest. ^'Potato Diseases. — It is estimated that the State of New York lost in 19 15, principally from late blight, about $20,000,000. This outbreak was wide- spread in the northern States and reduced the yields as shown below, in comparison with 1914. Other conditions than disease were relatively equal : Maine 10,000,000 bu. New Hampshire 1,200,000 Vermont 1,600,000 New York 30,000,000 Pennsylvania 8,000,000 Michigan 23,000,000 Wisconsin 1 1 ,700,000 "It is estimated that the market value of the potato crop in Aroostock County, Maine, in 19 15 was reduced about 10%, or $1,078,000, on account of the occurrence of the powdery scab disease. In some sections the reduction amounted to as much as 50%. "It is estimated that 50% of the potato crop in Idaho was injured by diseases last year and from 10% to 20% rendered wholly unsalable. The total an- nual loss in this State is estimated at $196,000. ''Sweet-Potato Diseases. — It is estimated that the annual loss due to sweet-potato diseases in the Preface ix United States is approximately $10,000,000. About $750,000 of this loss may be attributed to stem rot, the other important diseases being black rot, foot rot, and storage rots. ^^ Asparagus Rust. — Asparagus rust has practically destroyed all of the original plantings of asparagus and driven the old varieties out of cultivation. These have now been replaced by partially resistant kinds and the new strain bred by this Department is almost wholly resistant, so that in the near future these losses will be eliminated. Tests of some of the new rust-resisting strains in 191 5 showed gains over the standard varieties amounting to more than $200 per acre. '' Cowpea Diseases. — It is estimated that the an- nual saving as a result of the introduction of wilt and root-knot resistant cow-peas is $3,000,000." A conservative estimate of the money loss from diseases would be about 20% of the total value of the truck crops grown in the United States. Accord- ing to the estimate given on page vii, the total value of the truck crop in the United States in 1909 amounted to the sum of $301,104,144. If 20% of this was lost through damage from diseases, it will be seen that in 1909 the American truckers lost $60,220,828. This does not include the large losses from insect pests, nor losses incurred in storing, or in shipping truck produce. It is no exaggeration to state that if our present knowledge of Plant Pathology were made use of by truck farmers, nearly 80% of this loss could be X Preface prevented. Can any one say that such a saving would be insignificant, untimely, or unpatriotic? The present work has been prepared with the aim of stimulating more research in truck-crop diseases, and also of assisting the trucker to make use of our present knowledge, in order to prevent avoidable losses, increase the trucker's profits, and assure a greater food supply. The writer seriously solicits suggestions or criticisms on his work. Acknowledgments are due to Dr. and Mrs. D. de Sola Pool, of New York City, for the inspiration, the encouragement, and the valuable assistance rendered in the preparation of the manuscript, and later in reading and criticizing it. To Dr. E. A. Bessey of the Michigan Agricultural College, and to Dr. Mel. T. Cook of Rutgers College, the author owes hearty thanks for the careful reading and the valuable suggestions and criticisms which they have given this work. Acknowledgments are also due to Dr. G. H. Coons of the Michigan Agricultural College, to Prof. F. B. Paddock and to Mr. W. T. Brink of the Texas Agricultural Experimental Station for reading the manuscript and proof. Grateful appreciation is likewise due to Dr. I. Adlerblum of the Metropolitan Life Insurance Co. of New York City for criticizing the manuscript and proofs. For the use of illustrations the author is indebted : to Dr. G. P. Clinton; to Dr. Mel T. Cook; to Drs. G. H. Coons and E. Levin; to Dr. H. A. Edson; to Dr. B. B. Higgins; to Prof. H. S. Jackson; to Dr. L. R. Jones; to Dr. T. F. Manns; to Prof. A. V. Osmun; Preface xi to Prof. F. B. Paddock; to Prof. W. G. Sackett; to Prof. A. D. Selby; to Prof. R. E. Smith; to Prof. H. E. Stevens; to Prof. J. A. Stevenson; to Prof. D. B. Swingle; to Prof. DeVault and to Dr. F. A. Wolf. Last, but not least, grateful acknowledgments are due my wife Esther Michla Taubenhaus, whose de- votion to art and science, and whose inspiration made this work possible. J. J. Taubenhaus College Station, Texas January 22, igi8. PREFATORY NOTE With the greater specialization along all lines of industry the problems that confront such a specialist as the author of this book are felt more keenly and the necessary remedies are more fully appreciated. So there has grown up in the last few decades in this country a body of agricultural experts, the truck growers, who have found, as they have con- centrated their attention more and more inten- sively upon a limited number of crops, that they are paying a great tax in the shape of losses due to diseases. Probably, in fact we know that very often it certainly is the case, similar losses are suffered by general farmers, but with their large plantings and less intensive culture these losses are not appreciated as they are by the truck grower. Other factors, too, enter in. In general the truck crops occupy land near cities or which from its adaptability to special crops or from its accessibility to markets is accordingly more valuable than ordinary farm lands. Furthermore, the crops themselves have a greater monetary worth than the staple crops. Both these factors make the losses by plant diseases much more keenly felt. With this recogni- tion of the losses incurred has arisen a demand for xiv Prefatory Note help in the prevention of the diseases responsible for the damage. So plant pathologists have had to direct their attention to diseases of truck crops. The present book is an attempt by such a pathologist who has specialized along this line to meet the de- mand for help in the way of giving information as to the diseases occurring on truck crops and, so far as it is possible, telling how these losses may be pre- vented or at least reduced. The last quarter century has seen a marvelous development of that division of the science of Botany that is devoted to the study of plant diseases, Plant Pathology. As each crop has been given greater attention the number of diseases found to occur upon it has been amazing. Plants nearly related to each other may have some of their diseases in common, but even with very closely related species some of the troubles affecting them will be different. When we now consider the large number of crop plants that are the subject of intensive culture as truck crops, and note, furthermore, that they re- present the most diverse families of plants, it is not to be wondered at that the number of organisms causing diseases of truck crops is a large one. The author by grouping the crop plants together by their botanical affinities has taken full advantage of the fact that nearly related plants may suffer from some of the same diseases and thus has made it possible in some cases to consider such diseases only once for several different, but closely related, crops. Considerable attention is directed to the symptoms Prefatory Note xv by which the various diseases may be distinguished. These descriptions are made in non-technical lan- guage so that the practical grower can understand them and recognize the diseases in question. Besides this the methods of control are also described in popu- lar terms. The author's long study of the subject has made it possible for him to approach this part of the work from the standpoint of the grower, so that as far as possible the remedies or preventive measures recommended are those with which he has practical experience. Occasionally it is impossible to recom- mend a remedy since sometimes a disease is of such a nature that by the time it becomes apparent the damage is done. But even in such cases directions are given which will reduce the loss or at least permit its avoidance another season. The discus- sions as to the cause of the disease are unavoidably given in somewhat more technical form from the very nature of the case, especially where it is the question of diseases caused by fungi or bacteria for which brief scientific characterizations are neces- sary. These technical discussions are essential for pathologists and other students of the subject so that the book will be appreciated by Experiment Station workers. Extension Specialists, college stu- dents, and others, as well as by the truck growers themselves for whom the book is primarily intended. Ernst A. Bessey, Professor of Botany, Michigan Agricultural College. CONTENTS PART I CHAPTER I PAGE The Normal Soil and its Requirements . 3 CHAPTER II Sick Soils not Influenced by Parasites . 23 CHAPTER III Soil Sickness Due to the Presence of Para- sites Harmful to Plants . . .41 CHAPTER IV Methods of Treating Sick Soils ... 53 PART II CHAPTER V The Healthy Host and its Requirements . 63 CHAPTER VI Causes of Diseases in Crops . . .71 a. Diseases of a Mechanical Nature B. Diseases Due to Physiological Causes c. Diseases of Unknown Origin xviii Contents PAGE D. Diseases Due to Parasitic Bacteria or Fungi E. Diseases Induced by Parasitic Flowering Plants CHAPTER VII Poor Seed 92 PART III SPECIFIC DISEASES OF TRUCK CROPS CHAPTER VIII Family AoARiCACEiE 103 Diseases of the Mushroom CHAPTER IX Family Araliace^ 108 Diseases of the Ginseng CHAPTER X Family Chenopodiace^ 116 Diseases of the Beet Diseases of the Spinach CHAPTER XI Family Composite 137 Diseases of the Artichoke (Jerusalem) Diseases of the Artichoke (Globe) Diseases of the Lettuce Diseases of the Salsify- Diseases of the Sunflower Contents xix CHAPTER XII PAGE Family CoNVOLvuLACEiE , . . . .151 Diseases of the Sweet Potato CHAPTER Xin Family Crucifer^ ... ... 185 Diseases of the Cabbage Diseases of the Cauliflower Diseases of the Horse Radish Diseases of the Kale Diseases of the Mustard Diseases of the Radish Diseases of the Turnip CHAPTER XIV Family Cucurbitac^ . . . . .218 Diseases of the Cantaloupe Diseases of the Cucumber Diseases of the Citron Diseases of the Squash Diseases of the Watermelon CHAPTER XV Family Gramine^ ..... . 250 Diseases of the Sweet Corn CHAPTER XVI Family Labiate 255 Diseases of the Balm Diseases of the Catnip Diseases of the Horehound XX Contents Diseases of the Mint Diseases of the Peppermint CHAPTER XVII Family Leguminos^ .... 259 Diseases of the Bean Diseases of the Lima Bean Diseases of the Cow Fea Diseases of the Garden Pea CHAPTER XVIII Family Liliace^e , . . . . . 279 Diseases of the Asparagus Diseases of the Chive Diseases of the Onion CHAPTER XIX Family Malvace^ ...... 295 Diseases of the Okra CHAPTER XX Family Portulacace^ ..... 299 Diseases of the Purslane CHAPTER XXI Family Solanace^ ...... 300 Diseases of the Egg Plant Diseases of the Pepper Diseases of the Potato Diseases of the Tomato Contents xxi CHAPTER XXII PAGE Family Umbellifer^ . . . . .354 Diseases of the Carrot Diseases of the Celery Diseases of the Parsley Diseases of the Parsnip Weeds PART IV CHAPTER XXIII Methods of Control . . . . .361 CHAPTER XXIV Control of Insect Pests by Natural Factors 375 CHAPTER XXV Treatment of Fence Posts . . . .378 Glossary . . . . . . .381 Index 387 ILLUSTRATIONS FIG. PAOB I. Bacteria 4 2 Structure of Fungi .... II 3- Nitre-Sick Beet Field, Showing Barren Spots 25 4 Effect of Lime 27 5 Pythium deBaryanum .... 43 6 Rhizoctonia 45 7 Fusarium Wilt . 47 8 Nematode Root Knot .... 49 9 Inverted Pan for Steam Sterilization 55 10 Surface Watering, Showing Portable Spray Equipment Used in Gardens about Cold Frames and Hotbeds 55 II Watermelon Slice Showing Hail Injury 74 12. Lightning Injury in Potato Field. Drought Injury of Sweet Corn 13. Malnutrition, Showing a Cabbage Leaf Affected by the Disease . 14. Blossom Drop ..... 78 81 83' XXIV Illustrations FIG. I'AGE 15. Mosaic : H 16. Bean Seeds Affected with Anthracnose, Colletotrichum lindemuthianum ... 84 17. Dodder 9^ 18. Mycogone Disease of Mushrooms . . 105 19. Ginseng Diseases 109 20. Beet Diseases . . . . .119 21. Spinach Diseases 131 22. Lettuce Drop 143 23. Lettuce Diseases ..... 144 24. Southern Blight of the Salsify . . 148 25. Sweet Potato Diseases .... 152 26. Sweet Potato Diseases .... 159 27. Sweet Potato Diseases .... 167 28. Sweet Potato Diseases . . . .170 29. Sweet Potato Storage Houses . . 183 30. Cabbage Diseases ..... 187 31. Cabbage Diseases ..... 196 32. Cabbage Diseases ..... 198 33. Diseases of the Cauliflower and Radish 202 34. Cercospora Leaf Spot of Horse-Radish , 207 35. Radish Diseases . . . . .210 Illustrations XXV FIG. PAGE 36. Turnip Diseases . 215 37- Turnip Diseases . 217 38. Cantaloup Diseases . 221 39- Resistant Cantaloup Strain . . 228 40. Cucumber Diseases. . 230 41. Squash Diseases . 235 42. WATERilELON DISEASES . . 239 43- Watermelon Anthracnose . 241 44. Watermelon Diseases • 244 45. Sweet Corn Diseases • 251 46. Bean Diseases . . . . . 260 47- Bean Diseases . . . . . 262 48. Diseases of Lima Bean . . 267 49. Bean Diseases . . . . . 269 50. Diseases of the Cow Pea . 272 51. Diseases of the Garden Pea and 1 Bean. 274 52. Asparagus Diseases . 280 53. Onion Diseases . . . . . 285 54. Onion Diseases . . . . . 286 55- Diseases of the Okra . . 296 56. Eggplant Diseases . 302 37- Diseases of the Pepper . 305 XXVI Illustrations 58. Potato Diseases 59. Diseases of the Potato 60. 61 62 63 64 65 66 67 68 69 70 71 72 Pox OR Pit of the White Potato, Showing Different Stages of Infection . Potato Diseases .... Potato Diseases . . • , . Potato Diseases .... Tomato Diseases .... Tomato Diseases . . ... Tomato Diseases .... Tomato Diseases .... Sleeping Sickness of Tomato Celery Diseases .... Celery Diseases . . . . Spray Machinery . . . • Parasitized Insects. Treatment of Fence Posts ...... PAGE 314 315 322 325 331 340 346 347 351 352 356 357 372 '' 376 INTRODUCTION The present world crisis has suddenly transposed the farmer from his former modest and humble posi- tion into the ranks of our foremost national figures. To-day the services of the tiller of the land are at a premium. The heroes of the day are not only those who can shoulder a gun at the front, but also those who can produce the food necessary to feed the great civil and military armies in the field and at home. It is to the credit of the American people that they have realized that intelligent farming re- quires as much skill, thought, and energy as is re- quired to build up industries or to formulate laws of government. Of the many phases of agriculture, trucking be- longs to the highest forms of intensified farming. Whether it is conducted on a large or on a small scale, it requires a thorough knowledge of plant life. An intelligent understanding of crop rotation is essential for success. Someone has well said that the farmer may be judged intellectually by the system of rotation which he practices. Great skill is also required to keep the land in a state of production during the greater part of the year. This is espe- cially true for our Southern States. As a whole, xxviii Introduction therefore, successful truckers must be a highly intel- ligent class of agriculturists. In trucking, as in all intensive farming, the aim is to produce superior crops, embodying both high yield and good quality. This can be made possible only through intensive breeding and culture. Un- fortunately, however, improvement in quality and yield is often accompanied by a loss of natural vigor and of power of resistance to disease. The great problem of the trucker is twofold — that of striving for quantity and quality, while protecting his crops from disease. This latter phase has gener- ally been overlooked. We all realize to-day that it is necessary not only to produce two blades of grass where one grew before, as Dean Swift declared, but also to conserve it during growth and prevent it from being carried off by various diseases. The great fam- ine in Ireland in 1844 resulted from an epidemic of late blight which destroyed the potato crop. Such a condition could hardly occur to-day, because we now have a better knowledge of plant life, the causes which induce disease, and the methods of coping with it. Considerable research has been carried out on the diseases of truck crops. The work of Professors Stew- art, Selby, Jones, Orton, Clinton, Lutman, Melhus, Manns, Harter, Sackett, Whetzel, and of others has already yielded valuable information on the diseases and their control in the case of some of our staple food crops. Still, in the case of many diseases, little is known as yet as to methods of treatment. But much is to be looked for from research in the future. Introduction xxix It was the writer's intention to avoid technical terms as far as possible. However, it was found ex- tremely difficult to omit every trace of a technical vocabulary, inasmuch as the popular terms are not always adequate in identifying a disease or in de- scribing its causal organism. As far as was consistent all popular names were accepted and retained in this work. However, there are many diseases which have as yet no popular names. As an illustration may be mentioned certain spot diseases of particular hosts. These spots may be caused by different fungi and yet resemble each other. In such a case how are we to name these diseases ? The surest way to avoid confusion is to call the diseases by the name of the causal organism, such as Phyllosticta leaf spot, Cer- cospora leaf spot, etc. Professor Stevens has sug- gested that we name all diseases by the name of their causal organism and add to it the term "ose, " such as Phyllostictose, Cercosporose, Sclerotinose, etc. The writer has not adopted Stevens terminology. In many cases the popular name of a disease de- scribes it far better than a technical term can do. To drop altogether such valuable popular terminology would only confuse the practical man. For instance, the popular term for lettuce "drop" is far more sug- gestive than "Sclerotinose." From a practical consideration, the healthy plant is of greater importance than the disease. If we were to bend all our energ}'- and skill to safeguarding the health of our crops, we would not be pestered with diseases. This is the point of view of this work. XXX Introduction For this reason, too, much space has been given to a consideration of the healthy hosts and of the soil, the mother of all vegetation. For the sake of convenience, the crops here con- sidered have been taken up in the natural order of families to which they belong. The families have then been arranged in alphabetical order, and the crops in each family taken up alphabetically by their popular names. On the other hand, the diseases have been arranged according to their causes, classi- fied according to the system generally accepted by students in mycology. The present work is intended as a guide to the trucker and gardener, and to the student in Plant Pathology. It is the result of several years of re- search in truck crop diseases. Where information has been drawn from other sources full references have been given, so far as possible from the latest investigations. The writer has aimed at making this work as broad and as generally useful as possible rather than confining it to local interest. Because of the great economic importance of the subject of truck crop diseases, it is felt that the pres- ent work fills a timely want and needs no apology. We cannot expect a general text-book on Plant Path- ology to go into lengthy treatment of all plant dis- eases, and even less so with those of the trucking crops. The subject in itself is too important and too broad to be dealt with adequately in a few pages. The time will undoubtedly come when the diseases of every important crop will be treated separately in Introduction xxxi book form. The Culture and Diseases oj the Sweet Pea, by the writer, was an attempt in that direction. Meanwhile, until we have available the results of more extended researches on particular crops, the present work, it is hoped, will fill the gap. PART I CHAPTER I THE NORMAL SOIL AND ITS REQUIREMENTS The aim of this chapter is to study the conditions under which a healthy plant lives and grows. Such knowledge will prepare us to consider the causes or factors which are responsible for abnormalities and diseases. Plants are endowed with life, and to live they must have food. Part of the food is derived from the air, but they cannot subsist on air alone. The sustenance of plants is also derived from the soil. It is to be regretted that laymen often regard the soil as merely a conglomeration of inert particles of dead rock. If this were true, plant life would be an impossibility. It is because soils are teeming with various forms of organisms beneficial to them that plant life is made possible therein. The science of Soil Bacteriology, though still in its infancy, has already taught us much to help make the trucking business much more profitable and successful than it has been hitherto. Indeed we may judge a soil by the kind of flora which predominates there, and call it fertile and healthy when this germ life helps to make it a favor- 3 4 Diseases of Truck Crops able medium for the plants. On the contrary, we call it sick or poor when it teems with bacteria and fungi which act as parasites on plants, or when the beneficial ones are absent or perform their duties imperfectly. Structure and Life History of Bacteria The term bacteria (singular bacterium), or microbe, or germ, refers to the smallest microscopical form of plant life. As we shall see later, bacteria are but one of the many forms of life in the soil. The first man to recognize bacteria was Anton van Leeuwenhoek, a native of Holland, and a lens maker by trade. He made use of the microscope in testing materials for lens making. In 1675 he happened to mount in a drop of water some tartar which he scraped off from his teeth. To his great surprise he discovered mi- nute little "animals" which moved about in curious fashions. In 1882, Robert Koch succeeded in grow- ing bacteria artificially and outside their natural environment. Thus was laid the foundation of the modern science of Bacteriology. Bacteria are very simple in form. We recognize the rod-shaped known as Bacillus (fig. i a), the spherical form as Coccus (fig. i b), and the corkscrew or comma form as Spirillum (fig. i c). Bacteria are very minute. It would take about fifteen to twenty thousand individual bacteria placed end to end to make one inch in length. They occur, however, in tremendous numbers and this enables them to per- Fig. I. Bacteria. a. Rod shaped, h. coccus, c. spirillum, d. plate culture, showing bacterial colonies isolated from soil. Normal Soil and Its Requirements 5 form wonderful tasks, as we shall soon see. Bacteria multiply in the simplest ways. A single individual upon reaching maturity becomes constricted in the center, then divides in two, each part now becoming a separate individual capable of nutrition, growth, and multiplication. It has been estimated by scien- tists that division of a single individual takes place about every twenty minutes. Granting that this rate of division is uninterrupted for twenty-four hours, the descendants of one germ would be in round numbers 1,800,999 trillions. These when placed end to end would make a string two trillion miles long, or a thread long enough to go around the earth at the equator seventy million times. It would take a ray of light four months, traveling as it does, to pass from one end of it to another. Individual bacteria can be detected only with a compound microscope. When grown on artificial media and under aseptic conditions, all the descend- ants of a single parent cell live together and constitute a colony, which becomes visible to the naked eye as a creamy jellylike drop (fig. i d). Relationship of Bacteria to the Function of A Soil The health of a soil as shown in its fertility is in- timately connected with the kind of bacteria present in it. We are as yet in the dark as to the possible .%nction of numerous groups of the soil organisms. Bacteriologists are seeking to discover their proper 6 Diseases of Truck Crops functions. A recent exhaustive study' of Actinomy- ces, or thread bacteria, in the soil seems to show that they serve to decompose grass roots, being more numerous in sod than in cultivated land. Other groups of bacteria undoubtedly must perform other important functions. The mere presence of friendly bacteria in the soil, however, would be insufficient to assure the welfare of our cultivated lands. What concerns us most is the work that they perform. Most of the plant's food as it is found in the soil is in a crude and una- vailable form. The bits of mineral matter, the manure or fertilizer, in the truck patches all con- tain plant foods but in a form which plants cannot readily use; they must be softened and predigested and this work is done by the friendly organisms. Plant food is therefore directly dependent on the work of these minute scavengers. An intimate re- lation exists between the higher and the lower forms of plant life, the one depending on the other. Distribution of Soil Bacteria For a practical purpose we ought to know in what soil and at what depth the beneficial bacteria are most likely to abound. Since the presence of bac- teria is necessary to maintain the fertility of a normal healthy soil, it is essential to study the main factors that determine their increase or decrease. We can- not expect to find them equally distributed in differ- ' Conn, Joel H., New York (Geneva) Agr. Expt. Sta. Bui. 52 : 3-11, 1916. Normal Soil and Its Requirements 7 ent depths of the same soil. Brown ' has shown that bacteria are generally more abundant in the upper eight inches. Table i , adapted from Brown throws much light on this phase of the problem. Table i Bacteria as Found in Various Depths of Soil and Under Different Cropping Systems Bacteria per Gram of Air-Dry Soil Plot Lab. Depth of No.^ No. Sampling I II III IV Average 601 A 4 in. 2033000 1627000 1793000 1555000 1752000 B 8 in. 1437000 1211000 I 241000 1104000 1248250 C 12 in. 541000 567000 559000 525000 546000 D 16 in. 287000 292000 312000 302000 298250 E 20 in. 147000 1 54000 1 59000 154000 153500 F 24 in. 92300 96500 95100 91500 93850 G 30 in. 49900 46300 50900 46900 48500 H 36 in. 32900 30000 33100 30400 31600 602 A 4 in. 3102000 2870000 2917000 2947000 2959000 B 8 in. 2238000 2177000 2105000 2258000 2194500 C 12 in. 498000 531000 531000 528000 522000 D 16 in. 255000 328000 316000 314000 304250 E 20 in. 182000 192000 188000 177000 184750 F 24 in. 89200 93300 91600 88300 90600 G 30 in. 53300 54900 53100 5180c 54275 H 36 in. 31700 35700 34200 31300 33225 604 A 4 in. 4606000 3908000 4210000 3932000 4164000 B Sin. 3132000 2834000 2976000 2793000 2943750 C 12 in. I 016000 882000 901000 831000 907500 D 16 in. 320000 309000 31 1000 320000 315000 E 20 in. 155000 163000 156000 149000 155750 F 24 in. 89400 96100 92900 88900 91825 G 30 in. 51900 55800 55000 52400 53775 H 36 in. 35100 36600 34900 32600 34800 ' Brown, p. E., Iowa Agr. Expt.Sta. Research Bui. 8 : 283-321,1912. ' Plot No. 601. — Continuous com. 602. — 2-year rotation, com and oats. 604. — 3-year rotation, com, oats, and clover. 8 Diseases of Truck Crops In studying Table i we find that in every case there is a marked decrease in soil organisms with each increase in the depth of the soil tested. It was fur- ther found by Brown that the moisture content was higher for four inches than for a greater depth. It seems evident that the decrease of soil bacteria below twelve inches is dependent not so much on moisture but rather on a decrease of air in the lower substratum. It must not be expected that the data given in Table I are applicable to every locality. Differences in the mechanical and chemical composition of the soil and subsoil, differences in topography, climate, and weather conditions, will all no doubt tend to influence more or less the increase or decrease of bacteria. Influence of Depth of Cultivation on the Number of Soil Bacteria The work of King and Doryland' has shown that the depth of cultivation is a potent factor in influ- encing the number of bacteria in the soil. This is briefly summarized by them in Table 2. Table 2 Influence oj Depth of Cultivation on Soil Bacteria Silt- plowed 4 inches deep increases the number of bacteria. . 15.46% plowed 6 inches deep increases the number of bacteria . . 10.94% plowed 8 inches deep increases the number of bacteria. .24.20% plowed 10 inches deep increases the number of bacteria . . 26.89% ' King, W. E., and Doryland, Ch., Kansas Agr. Expt. Sta. Bui. 161 : 211-242, 1909. Normal Soil and Its Requirements 9 Sand — plowed 4 inches deep increases the number of bacteria. .35.06% plowed 6 inches deep increases the number of bacteria. . 13.53% plowed 8 inches deep increases the number of bacteria . .22.90% plowed 10 inches deep increases the number of bacteria . . 5.11% The Influence of Manure on the Number of Soil Bacteria Besides cultivation, there are other treatments which may lead to an increased bacterial flora in the soil. As shown by Temple' such a result is obtained through the application of manure. In working with a newly cleared sandy loam, and applying fresh cow manure (this included solid excreta and no bedding) , at the rate of ten tons per acre, Temple obtained the following results as shovv^n in Table 3. Table 3 Showing Number of Bacteria per Gram of Dry Soil Bate March 26, 1909. April I, 1909.. . April 9, 1909 . . April 15, 1909.. April 22, 1909. . April 29, 1909.. May 6, 1909 Soil No. 326 Soil No. 326a No Manure With Manure 1,220,000 1,220,000 1,633,000 4,300,000 6,120,000 14,000,000 3,780,000 10,610,000 2,730,000 5,860,000 2,770,000 3,340,000 5,510,000 5,190,000 As further evidence that manure increases the soil flora, Temple used a clay loam, dividing it in the following manner ; and treated as follows : ' Temple, J. C, Georgia Agr. Expt. Sta. Bui. 95 : 6-35, 191 1. lO Diseases of Truck Crops Plat No. I — Stable manure. Plat No. 4 — Sodium nitrate. Plat No. 5 — A complete fertilizer, PKN. Plat No. 6 — Nothing, check. The effect of these treatments is briefly sununarized in Table 4. Table 4 Colonies per Gram of Dry Soil Date Plat No. I Plat No. 4 Plat No. s Plat No. 6 Dec. 9, 1910 March 30, 191 1 May 26, 191 1 28,230,000 18,500,000 20,200,000 11,430,000 9,150,000 4,850,000 191850,000 8,040,000 6,720,000 8,250,000 6,240,000 5,010,000 The above Table shows that although sodium ni- trate or a complete fertilizer increases the soil flora, neither one can be compared to manure in efficiency. Structure and Life History of Fungi Besides bacteria of all sorts, our cultivated soils are also teeming with fungi. The true function of the latter remains to be studied. There seems no doubt, however, that certain fungi like certain bac- teria in the soil work on the organic and the mineral matter to make it available as plant food. Parasitic fungi depend for their food on living plants alto- gether. Examples of these are the Uredinales, the Fig. 2. Structure of Fungi. a. Fruiting branch of Penicillium, showing conidiophores and conidia, b. mycelium of Penicillium, c. an individual conidiophore and chain of conidia of Penicillium, d. two conidia of Penicillium, showing a.ttachment of spores in the chain, e. fertilization of female oogonium by male antheridium, /. mature oospore, g. fruiting stalks of Rhizo- pus, h. individual fruiting head of_ Rhizo- pus showing spores, i. sexual fertilization and k. zygospore of Rhizopus showing spores, /. perithecium, showing asci and ascospores, or winter spores, m. Pycnidium or sac in which the summer spores are borne. Normal Soil and Its Requirements n cause of the true rust diseases. Saprophytic fungi are those which depend for their food on the dead and decaying organic matter in the soil. Between these two extremes there are intermediaries. As an illus- tration of a soil fungus may be taken the ordinary blue mold, Penicillium expansum Lk. This organ- ism is made up of colorless feeding threads techni- cally known as hyphaj or mycelium (fig. 2 b). The spores, which correspond to the seed of higher plants, are borne on short stalks which bear broomlike tufts composed of chains of small bluish, round bodies, the spores (fig. 2 a-c). Fungi differ from the higher plants in their nu- trition and mode of reproduction. Fungi have no green coloring matter, chlorophyll, and are thus unable to manufacture their own carbon by the de- composition of carbon dioxide as do green plants. This is why fungi must depend for their supply of carbon on dead organic matter or on the higher plants. Unlike the green plants, fungi have no flowers and reproduce by means of spores (fig. 2 g-h). It has been estimated that over 61,000 species of fungi have been found and described on the higher plants. The Soil Bacteriologist however has scarcely touched on the soil fungi. .Fungi are classified according to the mode of spore formation. In some the spores are formed by a regular sexual union of a female egg known as oogon- ium and of a male element, the antheridium (fig. 2 e, i, k). The resultant fertilized spore egg is known as oospore (fig. 2 f). The latter germinates by sending 12 Diseases of Truck Crops out a germ tube, or as is more generally the case, by the outer wall dissolving and the inner mass breaking up into small bits of naked protoplasm known as zoospores. Most fungi have two spore stages, the summer form intended for rapid dissemination and spread, the winter form intended to carry it over through cold or any other unfavorable weather con- ditions. The term conidia is applied to all spore forms borne free on special fruiting stalks known as conidiophores (fig. 2 a). A pycnidium is a sac- like body (fig. 2 m) in which are borne the summer spores. A perithecium is a sac-like body (fig. 2 1) which bears the winter spores of certain fungi. Other terms here used in describing parts of fungi will be found in the glossary. Nature and Function of a Healthy Soil Flora The function of a normal soil is to provide avail- able plant food. About 95 per cent, of the com- bustible weight of a growing plant is made up of carbon, hydrogen, and oxygen and nitrogen. The remaining 5 per cent, constitutes the mineral or the ash of the plant. Carbon, hydrogen, and oxygen are taken in the form of carbonic acid and water; nitrogen from nitrates produced by bacteria out of organic matter of the soil. The ash or the mineral elements of the plant are taken directly from the soil. Neither the organic nor the mineral elements are in a form which plants can make use of until they have been acted on by certain definite organisms in the soil. Normal Soil and Its Requirements 13 A. The Transformation of Carbon Cellulose, which is but a form of carbon, consti- tutes a large per cent, of the woody tissue of plants. Soils contain large amounts of cellulose and this un- doubtedly helps to maintain their proper physical con- dition. Straw manure, or green vegetable matter all contain large amounts of cellulose. When it is in- corporated in the soil, living plants cannot make use of it, because of its complex form. It therefore must first undergo a certain decomposition. This is ac- complished by a group of soil bacteria known as Amylobacter . These feed on the dead vegetable cellulose, breaking it up and reducing it back to car- bon dioxide, hydrogen, and fatty acids. The carbon dioxide either returns to the air to replenish the at- mospheric supply, or unites with water to form car- bonic acid and soil carbonates. The carbon dioxide is taken in by the plants either directly from the air through the leaves, or from the soil in some carbon- ate form. Thus we see that it is not the cellulose nor the product of its decomposition that furnishes plant food, but certain inorganic elements which are set free in its decomposition. B. Elaboration of Available Nitrogen From the viewpoint of plant nutrition, nitrogen is unquestionably the most important of all elements. The nitrogen of the air, although totalling about 79 per cent, of it, is not in an available form. In the transformation of proteids into available nitrogen 14 Diseases of Truck Crops in the soil two definite processes take place, all thanks to the work of certain soil bacteria. 1. Ammonification. In this process, the soil bacteria attack the complex proteids and convert them into ammonia. The odor of ammonia from decomposed ' urea, manure, or any other organic matter is always an indication that ammonification takes place. According to Sackett' and others the ability to bring about this change is attributed to the following soil bacteria: Bacillus mycoides. Bacillus proteus vulgaris, Bacillus mesentericus vulgatus, Bacil- lus subtilis, Bacillus janthinus. Bacillus coli-communis. Bacillus megatherium. Bacillus fluorescens liquefaciens, Bacillus fluorescens putridus, and Sarcina lutea. 2. Nitrification. Both ammonia and ammonia compounds are forms of nitrogen that are not yet readily available to plants. They must be changed further into simpler compounds or, as the process is known, must undergo nitrification. The ammonia is first oxidized into nitrous acid and nitrates. This is accomplished by two species of soil bacteria, Nitrosomonas and Nitrosococcus. The nitrates are then oxidized into nitric acid and nitrates, through the work of the bacterium Nitrohacter. The nitrates are the only forms of nitrogen which plants can use. C. Action of Soil Flora on Mineral Substances We have already pointed out that the inert mineral substances in the soil are not in a form in which » Sackett, W. G., Colorado Agr. Expt. Sta. Bui. 196 : 3-39, 19 16. Normal Soil and Its Requirements 15 plants can readily assimilate them. These too must first be acted upon by certain soil bacteria. 1. Changes of Phosphates. Phosphates as they commonly occur in nature are but little soluble in water. This is why they cannot be used in their first form, although they are required by most plants. Soils deficient in this element may be improved by such fertilizers as superphosphate of lime, ground bone, phosphate rock, or Thomas slag. In the pro- cess of decomposition that organic matter must un- dergo as it becomes available for plant food, large quantities of carbon dioxide are liberated which unite with the water in the soil to form carbonic acid. This acid attacks the insoluble phosphates, trans- forms them into superphosphates, — the only form soluble in water, — and renders them available to plant life. 2. Changes in Potassium, Sulphur, and Iron. Like phosphorus, potassium, sulphur, and iron are made available for plants through the indirect action of soil bacteria. The carbon dioxide and other organic acids produced during the fermentation of organic matter, attack the potash feldspar which occurs in the soil. The product is potassium car- bonate which is soluble in water and hence readily taken up by plants. The nitric acid which is formed during nitrification may also combine with the raw potash in the soil forming potassium nitrate which is a form available for plants. As a result of the activity of soil bacteria, hydrogen sulphide is evolved from the decomposition of pro- i6 Diseases of Truck Crops teids. The sulphur may be further changed into sulphur dioxide, and, when combining with water and oxygen, into free sulphuric acid. The latter read- ily combines with calcium or magnesium, forming calcium or magnesium sulphate. The plant obtains sulphur for the construction of its proteids from some of the soluble sulphates. How TO Maintain the Fertility of Soils We have already seen that the fertility of a soil is directly dependent upon the activity of certain bene- ficial bacteria. The latter constitute the life of a soil. It is therefore evident that for a soil to produce its maximum, its germ flora must receive careful con- sideration at the hands of truckers and gardeners. We must at any cost encourage these organisms to do their full duty at all times. Should they cease activity the soil would become barren. There is no doubt that plants remove large quan- tities of plant food from the soil. Headen^ has cal- culated that for 80,000 tons of sugar beet, there are consumed as fertilizers, 331 tons of potash, worth $31,100; 71 tons of phosphoric acid worth $5,680; 160 tons of nitrogen worth $54,400, making a total of $91,180, or a trifle over one dollar per ton. What is true for the sugar beet is true for every other trucking crop. In other words, soil fertility is capa- ble of being exhausted. Most of it may be returned in the form of manure and chemical fertilizers, but » Headen, W. P., Colorado Agr. Expt. Sta. Bui. 99: 3-16, 1905. Normal Soil and Its Requirements 17 these are very expensive and reduce the net profit from the crops. The object of every intelligent trucker should therefore be to reduce his manure and fertilizer bills by encouraging his soil bacteria to man- ufacture the greatest amount of the available food which his crops require. Like any other living form these bacteria require certain conditions of life if they are to thrive. Maintaining the Nitrogen Supply The nitrifying bacteria are air-loving organisms. Hence the more aeration we give them, the more pro- nounced their activity. Schlosing' determined that when a soil was entirely void of oxygen the nitrates were reduced, and brought about an actual evolution of free nitrogen which is useless to the plant. With 1.5 per cent, of oxygen nitrification was marked. When 6 per cent, oxygen was added to the soil nitri- fication was more than doubled. It is therefore evident that cultivation which aims at soil aeration also accelerates nitrification. The effect of soil aeration cannot be too strongly emphasized. Ac- cording to Chester,^ every cultivation of the soil with its attendant aeration is equivalent to a dressing of nitrate of soda in its cheapest form. If we realized this, and that nitrate fertilizers are usually the most costly, the alert trucker would learn the economy of more cultivating. ' Schlosing, Compt. Rend. Acad. Sci. Paris, Ixxvii, 203-253. * Chester, F. D., Pa. State Dept. of Agr. Bui. 98: 9-88, 1912. i8 Diseases of Truck Crops Besides oxygen, the nitrifying organisms demand, as an indispensable condition for work, a sufficient moisture in the soil. In dry soils and during dry weather, nitrification is almost suspended within the upper layers of soil. A third important factor is the chemical reaction of the soil. The nitrifying organ- isms work best when the soil gives a slight alkaline reaction. Too much alkalinity, however, like too much acidity, is detrimental as we shall see further on. Nitrification is further dependent on soil temperature. At 99 degrees Fahrenheit it is at its highest. A de- gree less than 54 F. retards it considerably. At 122 degrees F. very little nitrate is produced, and at 131 degrees F. nitrification ceases entirely. The physical condition of the soil is another important element to be considered. The highest rate of nitrification is found in truck lands, that is, in the sandy loams. Nitrogen Fixation from the Air It has been the common knowledge of farmers and truckers that legume plants, such as peas and beans, cause the soil on which they are grown to become more productive. It is not necessary here to enter into an abstract discussion of this phenomenon. Suffice it to say, that science has definitely shown that there is a bacterial soil organism, Pseudomonas radicicola, which is capable of fixing the free nitro- gen from the air. This organism attacks the young rootlets of the legume crops as other parasitic forms also do. Its presence in the root results in a nodule Normal Soil and Its Requirements 19 or swelling. Soon, however, it loses its parasitic character and becomes an agent for fixing the free nitrogen of the air, which is then stored up in the root nodule. In this form the nitrogen is consumed by the plant itself. As far as is known, P. radicicola can thrive on the roots of legume plants only. The Rhode Island Experiment Station' has foimd that an acre of soy beans for Instance may fix about 1000 pounds of nitrogen from the air during a period of five years, or 200 pounds per year. One hundred and forty pounds of the 200 were removed with the crop, and 60 pounds remained in the field. Since one pound of nitrogen was worth at least i6c., 200 pounds would cost $32. We must not, of course, suppose that every acre of soy beans would produce 200 pounds of nitrogen every year. This would depend somewhat on the nature of the soil, the degree of moisture, the amount of ox3'^gen, and other condi- tions congenial or unfavorable. What is certain, however, is that every alert gardener and trucker should learn to use legumes more extensively in his system of cropping. Soils which have grown leguminous crops for a period of years are well supplied with P. radicicola. Other soils are deficient in it and must be artificially inoculated. The numerous types of pure cultures of the organism sold in liquid form have as a rule proven a failure. The organism dies out or loses its effectiveness in the artificial liquid media. The best forms of pure cultures now used are those grown on » Rhode Island Agr. Expt. Sta. Bui. 147. 20 Diseases of Truck Crops sterilized soil. This method has been developed at Cornell University, The soil is after all the natural and best medium where soil bacteria can grow. On it P. radicicola lives longer, and hence when it is used for inoculation, better success may be expected. The Alphano Humus Co. of New York City have on the market cans with sterilized soils, in which the legume bacteria have been introduced. Each can is sufficient to inoculate one acre of soil. The ability of the organism of one legume crop to inoculate another crop has long been a subject of discussion and has not as yet been satisfactorily answered. Carman and Didlake^ have shown that there exist six different species of legume organisms. For example they found that the organism of alfalfa is the same as or similar to the one which works on the sweet clover {Melilotus alba), trefoil or black medick {Melilotus lupulina), and bur clover {Melilotus denticulata) . This same organism, however, cannot produce nod- ules on the roots of any species of Trifolium, of Vicia, Pisum, Vigna, Glycine, or Phaseolus. The organisms of all the species of Trifolium (clover) are one and the same. The organisms of all the species of the vetch and garden pea are one and the same. They cannot work, however, on red or crimson clover, or on alfalfa. The cowpea organism seems to be adapted to the cowpea only. The same thing appears to be true for the soy bean organism and for that of the garden bean. Therefore when a land is to be inoculated • Garman, H. and Didlake, Mary, Kentucky Agr. Expt. Sta. Bui. 184: 343-363, 1914- Normal Soil and Its Requirements 21 with the garden bean organism, for instance, none must be used but those taken from the bean. Under ordinary conditions, where a soil is known to produce healthy crops of one (legume) variety, some of that soil may be used to inoculate other soils intended for the same crop. Economical Use of Commercial Fertilizer A knowledge of the functions of soil bacteria and a proper management of the soil means a saving of commercial fertilizer and the proper maintenance of soil fertility. In trucking more than in any other phase of farming, the soil is being made to produce the whole year around. This is especially true for our Southern States where the summer and fall seasons are longest, or where the winters are very mild. It, therefore, often becomes necessary to use chemical fertilizers to supplement the work of the soil bacteria. This is especially true for some par- ticular crops which draw heavily on certain mineral constituents. In order to obtain the greatest re- sults from the use of chemical fertilizers, the follow- ing items should be carefully considered. 1. The Location of the Field. Uplands or hillsides will require heavier application of fertilizer since some of it is likely to be carried off by washing. Lowlands, especially those near uplands which wash badly, generally require less. 2. The Character of the Soil. The chemical composition of the soil has a marked influence on the 22 Diseases of Truck Crops effect of fertilizers. A chemical analysis of the soil will enable the trucker to make a more economical use of his fertilizer. If a land, for instance, contains too much iron and aluminium, applied phosphate fertilizers may be modified into ferric and aluminium phosphate, which become slowly available to plants. On the other hand when phosphate fertilizers are changed in the soil into tricalcium phosphate it becomes available more readily. Sandy soils are generally quick to respond to fertilization; they can therefore stand heavier application than the cold clay soils vv^hich respond more slowly. In the latter, the fertilizers are likely to be converted into forms un- available to plants. The trucker should therefore avoid depending altogether on the use of chemical fertilizers. The best results are always obtained and the fertility of the soil best preserved when the use of chemical fertilizer is supplemented v/ith animal or green manures. CHAPTER II SICK SOILS NOT INFLUENCED BY PARASITES We have seen that a normal and healthy soil is one in which the beneficial soil flora is at its maximum of normal activity, making the food of the plant assimilable. We have to discuss the abnormal or sick soils now. In this class we include those which are either physically or chemically so constituted as to have a detrimental effect on the activity of the soil flora; and those which are overrun with organ- isms directly parasitic on the plants grown in that soil. There are five classes to be considered in the first division. I. Denitrified Soils This detrimental condition in the soil is brought about by a group of undesirable organisms, some of which are Bacillus ramosus, B. pestifer, B. mycoides, B. subiilis, B. mesenlericus vulgatus. In Chapter I we have seen that the nitrifying bacteria oxidize the nitrogen and make it avail- able for plants. In denitrification, the harmful bacteria tend to reconvert the available nitrogen into a non-available form, or else to liberate it into the air, where it may be considered as lost so 23 24 Diseases of Truck Crops far as the crops are concerned. Most trucking lands contain the nitrifying and denitrifying organ- isms in about equal proportions. To encourage the activity of the one over the other is the aim of intelligent trucking. The denitrifying bacteria thrive best in an abundance of carbohydrate foods. Fresh coarse manure with a high percentage of straw, when applied to the soil, will favor denitrification. It should therefore be avoided as far as is possible. There are, however, market gardeners who often use as much as fifty tons of such manure per acre in ad- dition to a nitrate fertilizer. Such action is very likely to encourage denitrification because of the large amount of carbohydrates incorporated in the soil. Indirectly denitrification will finally cause various physiological plant troubles, most of which are little understood. Poor growth and the shedding of blossoms will characterize plants deprived of avail- able nitrogen food. Denitrification may largely be prevented. A judicious use of manure, especially on the heavy soils, drainage, and proper tillage are all factors which induce nitrification, thereby also pre- venting denitrification. 2. Nitre-Sick Soils This form of sickness, peculiar to certain Colorado soils, was carefully studied by Headen^ and Sackett.^ Nitre-sick soils are those which contain such large quantities of nitrates that they inhibit plant growth. » Headen, W, P., Colorado Agr. Expt. Sta. Bui. 155. sSackett, W. G., Colorado Agr. Expt. Sta. Bui. 196:3-39, 1914. Fig. 3. NiTRE-vSicK Beet Field, Showing Barren .Spots. Sick Soils not Influenced by Parasites 25 Truck crops (fig. 3), grains, and fruit trees rapidly deteriorate on sucli lands. This condition occurs in a variety of soils in Colorado. It is met Vv'ith in the light sandy loams as well as in the heavy clay loams, on lowlands as well as on hilltops. It is to be dis- tinguished from true alkali troubles. The distinguishing characteristic of a nitre-sick soil is its brownish-black wet appearance. From afar the soil looks as if it had been wetted with crude oil ; however the soil is usually dry. Sometimes the soil may be moist and slippery, due no doubt to the presence of large quantities of deliquescent salts. Walking through such a field produces a sensation similar to that which one would get from walking on cornmeal or ashes. The accumulation of excessive amounts of nitrates in the soil is due to the activity of a bacterial soil organism, Azotohacter chroococcum. This organism has the power of fixing free nitrogen from the air and depositing it in the form of nitrates in the soil. The conditions which favor this activity still await study. Normally, soils contain from 140 to 150 pounds of nitrates per acre foot. In a nitre-sick soil, each acre foot contains 113,480 pounds, or 56.74 tons. With such a high concentration of nitrate, it is impossible for plants to grow. So far, we know of no methods to reclaim nitre-sick soils. 3. Acid-Sick Soils Soils which contain an excess of acid in which crops refuse to grow, may be termed acid-sick. Acids 26 Diseases of Truck Crops in soils have a directly poisonous effect on plants. Soil acidity may be brought about by the loss of lime and other bases ; and by the decomposition of organic and inorganic matter. Crops are known to draw heavily on the lime of the soil, and thus increase the proportion of acidity. This then is one direct way of depleting the soil lime. A ton of alfalfa, for instance, is known to take up 50 pounds of lime. With a yield of 6 tons per acre, the annual loss of lime per acre would be 2100 pounds. Lime and other bases are further lost from the soil by leaching. The soluble carbonates are but slowly soluble in pure water. However, carbon dioxide, nearly always present in soils, changes the calcium carbonate into calcium bicarbonate, which is rather soluble, and readily leaches out with the drainage water. Soils which are heavily manured are apt to become more acid. The decomposition of the organic matter yields large quantities of carbon dioxide which act on the carbonate in the manner above indicated. The annual leaching of lime from soils varies from I GO to 1000 pounds per acre. In addition to these causes, poor drainage has a tendency to increase the soil acidity. The application of ammonium sulphate as a fertilizer leads to a devel- opment of acidity by the production of sulphuric acid. The same is true when muriate of potash is added. In the process of nitrification in which nitrogen is made more available for plants, acids are produced. Acidity in a soil is usually characterized by a Ian- £i0.. TLl^ Fig. 4. Effect of Lime. a. to d. R hubarb, e. to ^. New Zealand Spinach, a. and 6., e. and /. both receiving sulphate of ammonia, a. and e. unlimed, 6. and/, limed, c. and y2 feet wide. A center aisle between the two rows of bins should be three feet wide. All these Fig. 29. Sweet Potato Storage Houses. a. An ideal large commercial dry kiln potato house, showing windows and top ventilators, b. a small poor potato house lacking means of ventilation, c. a close side view of the top of the ventilator shown at a. Family Convolvulacese 183 aisles should be converted into trap-doors of two pairs, at least i>2 feet wide, opening by means of weights either way from the center, and occupying the entire length. A series of roof ventilators should be provided, sufficient to carry off at least most of the moisture. In small houses there should be at least two such ventilators, each about three feet square and about five feet high. In medium sized houses there should be three of similar dimensions. In large houses from four to six ventilators should be provided (fig. 29 a and c). Where sweet potatoes are stored in bins, they should first be put into every other one, beginning with the lowest and finishing with the top floor. Thus the filled bins will have a chance to dry out. Bins deeper than seven feet should be divided by two partitions, leaving a two or three inch air space between them. The inner bins throughout should be filled first. It is a mistake to close doors and venti- lators when the potatoes are sweating, for during this stage all the ventilation possible should be given, even at night, provided of course that the temperature does not go so low as to cause chilling. Artificial Aids in Storage. Each floor should be provided with an accurate recording thermometer and hygrometer. With the help of these two instru- ments, the critical point of excess heat and moisture may be easily determined. It is possible that in order to bridge over these critical periods in storage some system of artificial drying may be required. This 184 Diseases of Truck Crops may be accomplished by the use of fans or blowers run by electricity or by a small gasoline motor. WEEDS There are but few weeds in this family which are subject to the same diseases as the sweet potato. The wild morning-glory (Ipomcea purpurea), the wild sweet potato {Ipomcea pandurata), and the small and great bindweed {Convolvulus arvensis and C. sepium) are all subject to black rot, SphcBronema fimbriatum. All these weeds are also attacked by white rust, Cystopus ipomcBce-pandurancE. Whether this rust is the same as the white rust of the sweet potato, or whether it is another physiological species or race, still remains to be determined. But in any case, these weeds must be kept out of sweet potato fields if we desire to keep the black rot of sweet potato in check. CHAPTER XIII FAMILY CRUCIFERiE This family ranks high in the number of impor- tant cultivated plants that it contains. Of the truck crops of economic importance may be men- tioned the Brussels sprouts, cabbage, cauliflower, col- lard, horseradish, kale, kohlrabi, mustard, radish, rutabaga, sweede, turnip, and watercress. According to the Thirteenth Census of the United States, the area devoted to cabbage in 1909 in all the States was 125,998 acres, and the total crop was val- ued at $9,719,641. The important cabbage States, ranked according to area, were as follows : New York, Wisconsin, Virginia, Ohio, Pennsylvania, Illinois, New Jersey, Texas, Michigan, California, Maryland, Florida, Colorado, Iowa, Massachusetts, Minne- sota, Louisiana, South Carolina, Mississippi, Ala- bama, Tennessee, and Kansas. States with less than 1000 acres are omitted. The total area of cauliflower in 1909 in the United States was estimated at 3466 acres and the total crop was valued at $602,885. The States which produced most of the crops are: New York, Cali- fornia, Illinois, Massachusetts, and Florida. 185 1 86 Diseases of Truck Crops The total 1909 area in horseradish was estimated at 1475 acres, and the total crop valued at $233,885. The crop is grown mostly in North Dakota, Pennsyl- vania, New York, New Jersey, and Illinois. The total 1909 area in kale was estimated at 1495 acres, and the total crop valued at $146,010. The crop is principally grown in Virginia, Kentucky, Maryland, and New York. The total 1909 area devoted to radish was esti- mated at 2269 acres, and the total crop valued at $293,062. The crop is grown in the following States, ranking in order according to acreage: New York, Alabama, Virginia, Illinois, Mississippi, Louisiana, Missouri, and Texas. DISEASES OF CABBAGE (Brassica oleracea) The cabbage, although a hardy plant, is neverthe- less subject to numerous diseases. Disease may re- duce the profits of the crop by fifty per cent., or even mean total failure. Club Root Caused by Plasmodiophora hrassicce Wor. Club root is a field disease only. Few plant dis- eases are as cosmopolitan as this trouble. It is found in many of the European countries, and in Australia, New Zealand, and in the United States. The loss from club root ranges from forty to seventy Fig. 30. Cabbage Diseases. a. Club root (after Cunningham), b. cell filled with spores of the club root or- ganism, c. spores and swarm spores of Plasmodiophora brassicce (b. and c. after Chuff), d. black rot of cabbage (after F. C. Stewart), e. individual black rot germs of Pseudomonas campeslris, f. black-leg on young cabbage seedling, g. black-leg lesion on foot of older cabbage plant, h. black-leg lesion on cabbage leaf, /. pycnidmm of Phoma oleracece, j. pycnosporvs of P. okracece (/'. and j. after Manns). Family Cruciferae 187 per cent, of the crop, although most of it may be prevented. Symptoms. Affected plants show a wilting of the foliage in the day, although recovering in the even- ing or during cloudy weather. Diseased plants are dwarfed, pale, and sickly looking. The seat of the trouble is at the roots. The latter swell considerably in size, often taking on the form of a hernia (fig. 30 a). The disease is more severe on seedlings in the seed bed, from whence it is carried to the field. The Organism. Club root is caused by a slime mold. The spores of the parasite (fig. 30 b) are nearly round and possess a transparent and refractive cell wall. According to Chupp, ' the first signs of germination are a swelling of the spores, followed later by a bulging at one side. The inner pressure exerted splits the spore wall, thus permitting the protoplasm (swarm spores) to ooze out. The latter is with- out a cell wall (fig. 30 c) , and is capable of motion by means of a thick flagellum at the small end. The germination of the spores is improved by exposing them for a short time to cold and drying. The best medium is water which has been filtered through muck soil. Infection of the host takes place through the wall of the root hair while the organism is in a uninucleate stage. Entrance of the parasite is evidenced by the browning and shriveling of the root hair. The dis- ease does not seem to be spread from place to place ' Chupp, Charles, New York (Cornell) Agr. Expt. Sta. Bui., 387 : 421-452, 19 1 7. 1 88 Diseases of Truck Crops by the wind. But infected manure in the seed bed will result in infected seedlings carrying the disease into a new field. Club root is known to attack a large number of cruciferous hosts, the more suscepti- ble of which include all of the cultivated species. Control. The best method of controlling club root is to grow cabbage on new land, or on land that was rotated with other crops, and given a rest from cruciferous crops for some time. Where it is not possible to do this, infected fields should be limed. Table 15, adapted from Cunningham,' clearly shows the effect of lime in controlling club root. From Table 15, it is seen that the use of fresh or air-slaked lime lowers the percentage of club root as compared with the calcium chloride on check plats. Moreover, when clubbing appeared in the limed areas, the disease seemed to be confined to the lowest roots and outside of the reach of lime. This then enabled the affected plants to make a crop in spite of the disease. The best effect of liming may be ex- pected when the lime is thoroughly incorporated in the soil to a depth of six to nine inches. As far as possible the trucker should avoid susceptible varieties of cabbage, among which may be mentioned: Mam- moth Rock Red, Dark Red Erfurt, American Savoy, Perfection Savoy, All Seasons, and Volga. Of the more resistant varieties of cabbage may be mentioned Hollander, Stone Mason, Large Late Flat Dutch, and Henderson's Early Summer. Finally, care ' Cunningham, L. C, Vermont Agr. Expt. Sta. Bui., 185 : 67-96, 1914. Family Cruciferas 189 1^0 •^ ^ 9^3y ^94 psqqnij irsfOO m «o °o . ^ItH^HS 32V}U3DX9J '^. . '^ . 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C/2 M 3 -S W) 02 --1 1/2 "i 3 •«* 3Sog3rlg:3go e ^^ al^XJjD^^'Q ^ 2 ooo^oo^o O* 10 lo 10 10 vo,Q 10 M «SPC^ M wCJ w »o 1 190 Diseases of Truck Crops should be taken to exclude club roots from the seed bed, since many an outbreak of this trouble may be traced back to the use of previously infected seedlings. Black Rot Caused by Pseudomonas campestris (Pammel) Ew. Sm. The disease is known to growers as stem rot and black rot. The latter perhaps is the more common name. The trouble may now be found wherever cabbage is grown on a large scale. Symptoms. Black rot has distinct symptoms which cannot easily be confused with other cabbage diseases. On the leaves, the symptoms are mani- fested as a burning appearance on the edges (fig. 30 d) and a yellowing of all the affected parts except the veins, which remain blackened. From the mar- gin of the leaves the disease works downwards to the stalk. From there the disease travels up again to the leaves and from there to the stems. The parasite works in the fibro-vascular bundles of the leaves and main stalk, causing a premature defoliation. Occa- sionally, the disease enters one side of the stalk, the latter becoming dwarfed and the cabbage head be- coming one sided. In severe cases of attack, there is a total lack of head formation. In splitting open a stump of an affected plant, we will find a black ring which would correspond to the places of the fibro- vascular bundles invaded by the organism. Smith ^ ' Smith, E. F., U. S. Dept. of Agr. Farmers Bui., 68: 5-21, 1898. Family Cruciferae 191 found that the infection takes place through small openings naturally found on the leaves and known as water pores which are found scattered over the teeth of the leaves. Infection by means of insect bites is also a very common occurrence. Outbreaks of black rot in new fields may undoubtedly be traced back to the use of infected manure. Black rot also at- tacks broccoli, Brussels sprouts, cauliflower, char- lock, coUard, kale, kohlrabi, black mustard, rape, rutabaga, radish, sweede, and turnip. The Organism. Pseudomo?ias campestris is a rod- shaped organism, slightly longer than it is broad. When young it is actively motile by means of long polar flagella (fig. 30 e) . It is found single or in pairs and produces no spores. It liquefies gelatine com- pletely in about fifteen days. On agar plates the col- onies are round, yellow in color, and the margin entire. On potatoes a copious growth is produced with no odor and no browning of substances. The in- vestigations of Harding' and others have proved that the black rot germ may be introduced into the seed bed and into new fields from infected cabbage patches. The virulence of black rot is largely de- pendent on the weather. It is unfortunate that favorable weather conditions for the cabbage plants are also favorable for the disease. Control. Before planting, cabbage seed should be disinfected for fifteen minutes in a solution of y^ pint of pure (40%) formaldehyde diluted in seven gallons ' Harding, H. A., New York (Geneva) Agr. Expt. Sta. Bui., 251: 178-194. 1904. 192 Diseases of Truck Crops of water. In making the seed bed, manure known to be free from cabbage refuse should be used . All insect pests should be kept in check by spraying, and no animals should be allowed to roam in sick patches. Insects and farm animals act as carriers of black rot. The disease cannot be controlled by merely cutting off diseased foliage. If anything, this operation aggravates the trouble. Diseased plants should be pulled out and destroyed. Crop rotation should be practiced wherever the disease is well established. Soft Rot Caused by Bacillus carotovorus Jones. Soft rot, although a field trouble, causes great damage to stored cabbage. The greatest losses are reported from New York and Wisconsin where cabbage is stored on a large scale. Symptoms. The disease is characterized by a soft, mushy to slimy decay of the entire plant. The dis- ease works very rapidly under favorable conditions of moisture and temperature. The causal organism can gain entrance only through a wound or bruise. Rough handling of the crop during hauling and stor- ing therefore opens the way to heavy infection and consequently loss from soft rot. The Organism. The Bacillus is rod-shaped, long or short, and usually formed in chains. It moves about by peritrichous flagella. It completely lique- Family Cruciferae 193 fies gelatine in about six days. Gas is produced with a majority of strains. Control. The greatest loss in storage occurs where the temperature is maintained much above the freez- ing point and where the facilities for ventilation are poor. To remedy this, the temperature, as far as possi- ble, should be maintained one or two degrees above freezing. The crop should be thoroughly dried and ex- posed to the sunlight before being entered into storage. Diseased fields should be rotated to other crops. Damping off Caused by Olpidium brassicce (Worr.) Dang. The symptoms of damping off are similar to those produced by Pythium de Baryanum, p. 43. The sporangia of the parasite may be found singly or in groups in each infected host cell. The zoospores are globose, uniciliate. The resting spores are globose, wrinkled, and star-like in appearance. The disease is found mostly in seed beds, where it does considerable damage. For methods of control see p. 43. White Rust Caused by Cystopus candidus (Pers.) Lev. White rust of cabbage is seldom troublesome enough to attract attention. The symptoms of the disease are the same as on other cruciferous hosts such as mustard or radish, p. 211. 13 194 Diseases of Truck Crops Downy Mildew Caused by Peronospora parasitica (Pers.) De By. Downy mildew, while a common field disease, causes considerable damage to young seedlings. It is characterized by whitish downy patches on the under side of the leaf. Seen from above, the af- fected areas are angular, pale yellow, and somewhat shrunken. The spots seem to be limited by the veins of the leaf. The disease is common in damp weather. Besides the cabbage, cauHflower, radish, turnips, and numerous other cruciferous hosts are known to be susceptible to downy mildew. The sporophores of the fungus are stout and ntunerously branched, each branch repeatedly forked. The tips of the smaller branches are slender and curved. The conidia are broadly elliptical, and the resting spores are globose and smooth, becoming wrinkled with age. In the seed bed or in the field, spraying with 4-4-50 Bordeaux will control the disease. The first application should be given as soon as the disease makes its appearance. Later the application will be governed by weather conditions. Drop Caused by Sclerotinia libertiana Fckl. Drop is a disease fairly common on cabbage. The trouble may be recognized by a drooping and wilting Family Cruciferae 195 of the leaves. The bases of the affected foliage are covered with a white weft of mycelial growth, later by sclerotia. For a more extended discussion of the disease see lettuce drop, p. 143. Black Leg or Foot Rot Caused by Phoma oleracea Sacc. Black leg, first noticed in the United States by Manns ^ in Ohio, was undoubtedly introduced here from Europe. Symptoms. The disease is usually manifested in the seed bed about two to three weeks before trans- planting in the field. The trouble at first appears as white elongated sunken lesions on the stem and below the leaf attachment (fig. 30 f). Scattered over the lesions are minute black specks which constitute the pycnidia or fruiting sacs of the fungus (fig. 30 i and j). Infected seedlings usually collapse and take on a bluish color. In the field, the foliage of the older but affected plants (fig. 30 h) usually take on a mottled, metallic, bluish-red color at the margins, and the lower outer leaves wilt. On examining such plants there will always be found sunken lesions (fig. 30 g) which often girdle the foot of the plant. In wet weather affected plants attempt to produce new roots above the infected area, which, however, are never able sufficiently to support the plant. Foot rot is often confused with forms of injury brought about by maggots. ' Manns, T. F., Ohio Agr. Expt. Sta. Bui., 228: 255-297, 191 1. 196 Diseases of Truck Crops Treatment. Manns recommends treatment of the seed bed with 4-4-50 Bordeaux to be applied im- mediately after planting, at the rate of one gallon to each ten square feet of bed space. The bed is again sprayed with Bordeaux about two weeks before and once again at transplanting. Black Mold Caused by Alternaria brassicm (Berk.) Sacc. Black mold is a serious disease of the cabbage in the Southern States. It also attacks collards. Symptoms. Affected leaves are covered with spots which are nearly black on the under side of the leaf. The spots are composed of a series of rings, the smaller ones enclosed within the larger (fig. 31a). There is no distinct border separating the diseased from the healthy, the spots gradually shading off into the healthy tissue. Little is known of the causa- tive fungus or of the control of this disease. It is probable that spraying with 4-4-50 Bordeaux will be of value. Leaf Spot Caused by Cercospora hloxami B. and Br. Leaf spot is of little economic importance. It only attacks the leaves of weak or languid plants. The spots are pale, somewhat circular, surrounded by a slightly raised, faintly purple border. The conidial Fig. 31. Cabbage Diseases. a. Alternaria black mold. b. cabbage seedlings growing in a cabbage sick soil which has been steam sterilized, c. sick cabbage seedlings in a cabbage sick soil, (after Jones and Oilman), McCulloch, Lucia, U. S. Dept. of Agr. Bur. PI. Ind. Bui. 225 : 7- 15, 1911. Fig. 33. Diseases of the Cauliflower axd Radish. a. Spot disease of cauliflower (after McCuIloch), b. white rust of radish, c. conidio- phore of the white rust fungus, Cyslopus candidus, d. fertilization in Albugo Candida, e. germination of the oospore of Albugo Candida, f. ring spot on cauliflower head, g! perithecium of Mycospho'reUa brassicicola, h. ascus of Mycospha-rella brassicicola, i. ascospores of Mycosphcerella brassicicola {g. to i. after Osmun and Anderson). Family Cruciferae 203 The diseased leaves become yellow and drop off prematurel}^ The trouble apparently does not at- tack the cauliflower head. The same disease may also attack cabbage, but not radish, rutabaga turnip, or mustard. The Organism. Pseudomonas maculicola is a rod-shaped organism, with rounded ends, usually forming long chains in certain media, but producing no spores. The organism is actively motile by means of polar flagella. Involution forms are produced in alkaline beef bouillon; and pseudo-zoogloe^ occur in acid beef bouillon. No gas is produced and the organism is aerobic, and is killed by drying and exposure to light. Control. Badly diseased plants should be pulled up and destroyed. Spraying with 4-4-50 Bordeaux is recommended. In spraying cauliflower with copper compounds, and especially if the latter are in a concentration somewhat stronger than the plant can stand, numerous warts will appear on the leaves in about three days after spraying. These warts should not be mistaken for a disease induced by a parasitic organism. The wart formation is appar- ently due to a stimulation by the salts absorbed by the host cells. Von Schrenk' found that warts on cauli- flower leaves may be readily produced by spraying them with a solution made up of 5 oz. copper car- bonate dissolved in a mixture of three pints of am- monia to fifty gallons of water. He further found ' Von Schrenk, H., Missouri Bot. Gard., i6th Ann. Rept. : 125, 1905. 204 Diseases of Truck Crops that leaf warts may be produced by spraying with weak solutions of copper chloride, copper acetate, copper nitrate, and copper sulphate. Ring Spot Caused by Mycosphcerella hrassicola (Duby) Lind. The exact distribution of this disease is as yet un- known. The trouble was studied by Osmun and Anderson^ on cauliflowers shipped from California to Boston. Symptoms. On the leaves, the disease appears as numerous small spots and the affected foliage turns yellow. Most of the spots are formed on the laminae, but others are also formed on the large midribs. The spots are definite in outline, round and visible on both surfaces of the leaf (fig. 33 f). The color is light brown to gray, with dry centers surrounded by olive green or blue green borders which shade off in the natural color of the leaf. The outer edge of the spot is covered with the fruit of the fungus (fig. 33 g-i). Ring spot also attacks the cabbage. Spray- ing with 4-4-50 Bordeaux is recommended. DISEASES OF THE HORSERADISH {Cochlearia armoracia) The horseradish is generally considered a hardy plant. However, it is subject to numerous diseases. ' Osmun, A. V., and Anderson, P. G., Phylopath. 5: 260-265,1915. Family Cruciferas 205 The black rot, Pseiidomonas campestris, is the same as that of the cabbage, p. 190, and the white rust, Cystopus candidus, is the same as that of the mus- tard, p. 211, Root Rot Caused by Thielavia basicola (B. and Br.) Zopf. Root rot of horseradish is of Httle economic im- portance. The disease is confined to the roots of the plant. In advanced stages the normal root system may be entirely lacking, leaving a charred, blackened stub. New roots are constantly formed above the diseased area, but these in turn become affected and die. It is these new roots which the plant attempts to produce that manage to keep the infected host alive in a stunted and useless form. For a description of the organism and methods of control, see p. 275. AscocHYTA Leaf Spot Caused by Ascochyta armoracicB Fckl. This form of leaf spot is rather scarce in the United States and may be easily overlooked. The disease is manifested as brownish leaf spots of various sizes. Within the spots numerous pycnidia are formed which bear numerous elliptic-oblong, hyaline one- septate spores. 2o6 Diseases of Truck Crops Shot Hole Caused by Septoria armoracicz Sacc. Shot hole is a very serious disease which attacks the foliage of horseradish. Diseased leaves turn yellow and become peppered with round spots, whitish in the center, surrounded by a pale yellow border. The spots drop out and give the leaves a ragged shaggy appearance. The pycnidia of the fungus are formed in the center of the spots previous to their dropping out or on the remaining margin of the spot. Macrosporium Black Mold Caused by Macrosporium herculeum E. and M. This mold is confined to the leaves only. Late in the summer the leaves are attacked by round spots which at first are whitish, and later become coated with a black mold made up of the spore bodies of the fungus. Horseradish may also be attacked by another form of black mold, Alternaria brassiccB (Berk.) Sacc, see p. 196. White Mold Caused by Ramularia armor acicB Fckl. White mold is frequently met with on foliage of the horseradish. The spots are indefinite, irregular, Fig. 34. Cercospora Leaf vSpot OF Horse Radish. Family Cruciferae 207 and usually occupy large areas of the leaf. At first they are yellowish red in color ; but they become gray with age. Leaf Spot Caused by Cercospora armoracice Sacc. Leaf spot is characterized by pale spots on the leaves (fig. 34). The spots are usually confined to weakened leaves. The disease is of no importance. Control. Usually the diseases of the horseradish are not serious enough to warrant treatment. How- ever, when the crop is grown on a large scale, it should not be planted anywhere near cabbage or other cruciferous plants in order to protect it from black rot. If any of the leaf spots become serious the affected parts may be removed and destroyed and the plants sprayed with 4-4-50 Bordeaux. The plants should be carefully cultivated and fertilized in order to maintain their vigor, thereby also preventing the leaf diseases from getting troublesome. DISEASES OF THE KALE {Brassica oleracea var. acephala) Kale is considered a very hardy plant ; it is, however, subject to black rot, Pseudomonas campestris (Pam.) Ew. Sm. On the leaves, black rot is characterized by dark discoloration of the veins, and on the root, 2o8 Diseases of Truck Crops by a blackening and decaying of the stem; see also p. 190. Kale is also attacked by club root Plas- modiophora brassicce Wor., see p. 186. DISEASES OF THE MUSTARD {Brassica Japonica) Garden mustard Brassica Japonica is cultivated for its foliage. It is used as a green, relished for its edible qualities, and as a spring tonic. Mustard is subject to the following diseases: Black Rot, see Cabbage, p. 190. Club Root, see Cabbage, p. 186. White Rust (fig. 35 b-e), see Radish, p. 193. DISEASES OF THE RADISH {Raphanus sativus) Radish is subject to many diseases in common with the cabbage and numerous other crucifers. Club Root, see Cabbage, p. 186. Black Rot Caxisedhy Psendomonas campestris (Pam.) Ew. Sm. Black rot on radish is confined mostly to the tender white-rooted varieties, especially the Icicle. The black-rot germ penetrates the lateral feeding rootlets, from which it works its way in the main root. In cutting across a diseased radish, its interior fibro- vascular bundles are found to be blackened. Such Family Cruciferae 209 radishes are useless for the market. The disease seldom attacks the red or the black-skinned varieties. For further consideration of black rot see p. 190. Scab Caused by Actinomyces chromogenus Gasp. Scab is not a common field disease of radishes. It is, however, found to be troublesome on the crop grown in greenhouses. The French Breakfast is commonly susceptible to the disease. The trouble may be expected if the crop is planted in a soil which previously produced a potato crop that was badly scabbed or where infected manure was used, or too much lime applied. For further description of scab, see p. 317. Damping Off Caused by Rheosporangium aphanidermatum Ed. This disease, which was studied and described by Edson,^ is very troublesome, attacking radish and beet seedlings alike. Symptoms. The disease is confined to the root system, seldom appearing above ground. Diseased plants have a flabby appearance, and the normal green of the foliage is displaced by a slightly yellowish tinge. ' Edson, H. A., U. S. Dept. of Agr., Jour. Agr. Research, 4: 279- 292, 1915. 14 2IO Diseases of Truck Crops In severe cases the entire stand may be wiped out. On carefully pulling out a diseased plant, we shall find the side rootlets blackened, shriveled, and dead (fig- 35 a). Frequently the plant attempts to pro- duce new roots above the diseased area. In this case, however, there is only partial recovery. The disease is most prevalent in the heavy soils. The Organism. In general characters, the organ- ism may be mistaken for Pythium de Baryanum, but it differs from the latter in its asexual fruiting bodies. The mycelium of Rheosporangium aphanidermatum is hyaline, non-septate (fig. 35 c), and grows profusely on solid media. Mycelium of cultures one or two days old exhibits considerable streaming of proto- plasm which seems always directed toward the tip end of the hyphse. This protoplasmic streaming results in the final accumulation in protoplasmic material, and in consequence of a considerable en- largement of the tip of the thread. Finally a cell wall is laid down which cuts off the swollen portion from the rest of the mycelium. This swollen body which Edson named presoporangium (fig. 35 b) has the appearance of a zoosporangium but in reality it differs from it since it gives rise not to zoospores, as might be expected, but to an independent body which later gives rise to zoospores. The pre- soporangium now absorbs water and its outer wall ruptures, from which is seen to flow out a mass of protoplasm enclosed in a thin cell wall. This es- caped mass is really the young zoosporangium, the cytoplasm of which finally cleaves into zoospores. Fig. 35. Radish Diseases. a. Young radishes attacked by Rheosporangium damping off, h. presporangium, C. mycelium of Rheosporangium aphanidermatum. d. fertilization of the female oogonium by the male antheridium, e. mature oospore, /. root knot (h to e after Edson). Family Cruciferae 211 With the maturity of the sporangium its cell wall dissolves, liberating the swarm spores which swim about for a time, then come to rest, round up, and increase in size and germinate by sending out a germ tube. Oospores are produced in a fashion somewhat similar to Pythium. The oogonia are formed as terminal spherical bodies. The antheridium de- velops terminally, lying close to the oogonium. The content of the antheridium is emptied into the body of the oogonium (fig. 35 d) and fertilization is effected. The mature oospore (fig. 35 e) is spherical with a thick smooth or undulated wall and germin- ates by means of a germ tube. Control. When the disease is present on a large scale, it is useless to attempt to control it. The fungus, as we have seen, is a soil parasite, hence soil treatments discussed on p. 53 could not be consid- ered on a large scale. As far as we know, this disease attacks only radish and beet seedlings. Badly in- fected fields should be devoted to other crops for several years until the parasite is starved out. On a small scale, infected soils may be treated with formaldehyde (see p. 53), or fire (see p. 56). Downy Mildew, see Cabbage, p. 194. White Rust Caused by Cystopus candidus (Pers.) Lev. The damage caused by white rust depends largely on seasonal conditions. The disease is most preva- 212 Diseases of Truck Crops lent on early spring or fall radish. The greatest damage done by this trouble is to the seed crop. Symptoms. On the leaves, white rust is manifested as white raised pimples or sori (fig. 33 b) character- istic of all white rusts. When the surface of the sori breaks open a white powder, which consists of the spores of the fungus, is liberated. On the flower organs of the radish, the symptoms of the disease are especially striking. The ovary sacs, the stamens, corolla, and calyx become hypertrophied and dis- tended, resembling abnormal leaves. It has been questioned whether the white rust of the radish is the same as that which attacks other crucifers such as cabbage, mustard, etc. While much remains to be learned, the investigations of Melhus throw much light on the subject. Melhus* had no trouble in infecting the rat-tail radish (Raph- anus caudatus) with conidia taken from ordinary radish (Raphanus sativus). Melhus also secured infection by sowing conidia from the radish on white mustard (Brassica alba) and cabbage {Brassica oleracea). At no time, however, was it possible to infect more than fifty per cent, of the cotyledons or leaves of the white mustard which were inoculated. With the cabbage it was still more difficult to secure infection. Of the fifteen varieties inoculated less than one per cent, of the plants became infected. No infection could be obtained when sowing spores of Cystopus candidus from radish on ten varieties of ' Melhus, T. E., Wisconsin Agr. Expt. Sta. Research Bui., 15: 25- 83,1911. Family Cruciferae 213 turnips (Brassica rapa), black mustard (Brassica nigra), rutabaga {Brassica campestris) , shepherd's purse {Capsella bursa-pastoris) , garden cress (Le- pidium sativum) , wild pepper grass {Lepidium virgini- cum), hedge mustard (Sisymbrium officinale and S. altissimum), candy- tuft {Iberis umbellata), water cress {Nasturtium officinale), and wall flower {Cheiranthus cheiri). From the above experiments, it would seem that in dealing with the white rust fungus, Cystopus candidus, it is possible that there exist distinct races or strains, all of which are specialized to certain special hosts of the various crucifers. The best infection is secured when the seedlings of the host plant are chilled. This is why white rust is more prevalent in cool seasons. The Organism. Cystopus candidus has two fruit- ing stages. The summer or conidial stage is made up of simple chains of spores (fig. 33 c). The latter are separated one from the other by a minute beak-like projection. Each spore or zoosporangium germi- nates by six or more swarm spores, or zoospores. These, when set free, swim around, then come to rest and germinate by means of a germ tube. The oospore or sexual spore of the Cystopus is formed later in the season. The oogonia and antheridia (fig. 33 d) are developed within the infected host tissue. Fertilization proceeds in the same way as in Py thium. The mature oospore has a thick, sculptured wall, and is brown in color. The oospores germinate in the same way as the zoosporangium, i. e., by the forma- tion of zoospores (fig. 33 e). 214 Diseases of Truck Crops Control. Burning of all infected trash and crop rotation are the best effective remedies. Root Rot, see Beet p. 122, 128. Root Knot (fig. 35 f), see Beet p. 129. DISEASES OF THE TURNIP {Brassica Rapa) Club Root, s9e Cabbage, p. 186. Black Rot Caused by Psetidomonas campestris (Pam.) Ew. Sm. Black rot in turnips is apparently confined to the roots. Infected plants may live a long time, and show no symptoms on the leaves. The roots of such plants, however, are stunted, abnormal in shape, and very narrow. The interior tissue is dry rotted and blackened, emitting a characteristic strong odor. For further description of the black rot, see p. 317. Scab, see Beet, p. 120, and Potato p. 317. White Rust, see Radish, p. 211. Downy Mildew, see Cabbage p. 194. Drop (fig. 36 g), see Cabbage, p. 194. Anthracnose Caused by Colletotrichum Higginsianum Sacc. Anthracnose is a new disease which has recently been studied and described by Higgins^ in Georgia. ' Higgins, B. B., U. S. Dept. of Agr., Jour, of Agr. Research, lo: 157-161, 1917. Fig. 36. Turnip Diseases. a. and b. Anthracnose, c. cross section through acervulus, d. anthracnose spores, e. Cylindrosporium leaf spot, /. Phoma rot, g. Sclerotinia rot (c and d. after Higgins). Family Cruciferae 215 The disease attacks the leaves (fig. 36 a-b), causing small circular gray or straw-colored spots. The acervuli and the salmon-pink spore clusters appear only under moist conditions. The causative fungus differs from Colletotrichum brassiccB Sch. and Sacc. The acervuli are small, scattered on both surfaces of the spots. The conidiophores are short (fig. 36 c), conidia hyaline cylindrical one celled (fig. 36 d), setse dark brown to black, slender, i to 3 septate (fig. 36 c). On the stems the spots are more elongated. On the leaves the spots are said to be much smaller than those produced by CyUndrosporium brassiccB F. and R. (fig. 36 e). Anthracnose is not carried with the seed. No method of control is as yet known. Phoma Rot Caused by Phoma napobrassiccB Rost. Phoma rot is a disease which is common in the north of England. It is also found in New Zealand and in Canada. In the United States it has been reported but once, by Clinton^ of Connecticut. Phoma rot seems to be a storage trouble, although the disease is first introduced from the field. Symptoms. In the field, the disease is first noticed at digging as a rot around the crown, the top of the plant readily pulling off. In storage the disease is 'Clinton, G. P., Connecticut Agr. Expt. Sta.., 2,6th. Ann. Rept. : 355-358. 1912. 2i6 Diseases of Truck Crops manifested on the roots as a dry rot which appears first as scattered sunken spots bordered by dark areas (fig. 36 f). The pycnidia of the fungus are generally absent from the spots, but they appear in great abundance when the roots are placed under favor- able conditions of moisture. Control. It is doubtful if Phoma rot can be con- trolled by spraying the foliage in the field. Since the disease is carried over in the roots, it would be dangerous to feed them to stock or dump them on the manure pile. Rotation should be practiced where the disease has appeared more than once in the same field. Care should be taken that no diseased roots be permitted to enter the storage house or cellar. The roots should be thoroughly dried before storing, and the house or cellar should be kept moder- ately cool and ventilation resorted to wherever possible. Powdery Mildew Caused by Erysiphe polygoni D. C. Powdery mildew has not been known to cause any considerable damage to turnips in the United States. It is characterized by the presence of powdery white patches on both surfaces of the leaf. Besides affecting the turnip, Erysiphe polygoni has been recorded on about three hundred different hosts, especially the garden pea. For methods of control, see p. 367. Fig. 37. Turnip Disease. a. Macrosporium leaf spot, b. Macrosporium herciileum, showing conidiophores and conidia, c. individual conidium of M. herculeum (u. to c. after F. C. Stewart). Family Cruciferae 217 Macrosporium Leaf Spot Caused by Macrosporium herculeum E. and M. Leaf spot often attacks the flat turnip and horse- radish. On turnips it is manifested as brittle circular spots on the leaf (fig. 37 a). When numerous, the spots usually fall out, giving a shot-hole appearance. The long club-shaped spores (fig. 2>7 c) of the fungus are borne on long conidiophores (fig. 37 b) on the exterior of the dead tissue. Should treatment seem advisable, spraying with Bordeaux mixture is re- commended. Weeds Of the many cruciferous weeds which truckers have to contend with, the following few may be mentioned: Winter cress {Barbarea vulgaris), shepherd's purse {Capsella bursa-pastoris), cow cress {Lepidium catn- pestre), pepper grass {Lepidium virginicum). The above mentioned weeds and many other crucifers are subject to club root, black rot, white rust, and downy mildew. It is evident therefore that clean culture is impor- tant. These weeds must not be tolerated if we are completely to eradicate the diseases of the cultivated crucifers. CHAPTER XIV FAMILY CUCURBITACE^ The Cucurbit family contains numerous valuable truck crops. Those grown for their economic value may be mentioned: cantaloupe, cucumber, pumpkin, squash, and watermelon. According to the Thir- teenth Census of the United States, the total area devoted to cantaloupes and muskmelons in America was 52,419 acres, and the total crop valued at $3,604,636. The States, ranked according to the acreage devoted to these crops, were California, New Mexico, New Jersey, Indiana, Maryland, Florida, Georgia, Illinois, North Carolina, Michigan, Colorado, Missouri, Texas, Ohio, Tennessee, and Delaware. States with less than one thousand acres are omitted. The total area in the United States in 1909 given up to cucumbers was estimated at 32,310 acres, and the total crop valued at $2,719,340. The States ranked according to the area devoted to cucumbers were Michigan, New York, Illinois, Indiana, Florida, Virginia, New Jersey, Wisconsin, Texas, and Min- nesota. States with less than one thousand acres are omitted. 3l8 Family Cucurbitaceae 219 The total area devoted to watermelons in the United States in 1909 was estimated at 137,005 acres, and the total crop valued at $4,453,101. The States which lead in rank according to acreage devoted to watermelon were: Texas, Florida, Georgia, Missouri, Indiana, Illinois, California, Oklahoma, North Caro- Hna, South Carolina, Alabama, Iowa, Arkansas, Kansas, Virginia, Tennessee, Maryland, New Jersey, Mississippi, Kentucky, and Louisiana. DISEASES OF THE CANTALOUPE (Cucumis melo) The cantaloupe is subject to numerous diseases which often reduce the jrield of the crop and en- tail heavy money losses. Fortunately most of the diseases may be controlled. Bacterial Wilt Caused by Bacillus tracheiphilus Ew. Sm. Bacterial wilt may be regarded as one of the most serious diseases of the cantaloupe. It has a very wide distribution, but it is said to be restricted in its Southern distribution. The same disease also at- tacks the cucumber, pumpkin, and squashes. The trouble is not known to occur on hosts outside of the Cucurbitaceae. Even in this family there are plants which are not subject to its attack. Dr. Erwin Smith succeeded in artificially inoculating the fol- lowing cucurbits : Cucumis odoratissimus, C. anguria, 220 Diseases of Truck Crops Benincasa cerifera, Cucurbita fostidissima, C. cali- fornica, Echinocystis lobata. Symptoms. The symptoms of bacterial wilt are very striking. At first a few leaves of the plant are wilted. Soon after the entire plant wilts and dies. In cutting through an infected stem, a whitish viscid exudate oozes out from the vascular bundles of the cut surface. In placing one finger on the viscid substance and then gently removing it, the bac- teria will be strung out into numerous delicate threads resembling cobwebs. The disease works quickly and the change of leaf color from bright to dull green is also' sudden. Cantaloupes, unlike squash, show no tendency to recover temporarily from wilt. Bacterial wilt is spread about through the bites of leaf-eating beetles, such as striped cucumber beetle, {Diahrotica vittata). The Organism. B. tracheiphilus is a short straight rod with rounded ends. The organism occurs singly in pairs and rarely in chains of four; it is motile by means of flagella. It grows slowly on gelatine which is not liquefied. On potato cylinders growth is vigor- ous, resulting in a gray-white film with no changes manifested in the substratum. There is no gas pro- duction and the organism is aeorobic. Control. Infection begins at a place of injury produced by the bite or puncture of insects. Hence any attempt at controlling wilt should first aim at controlling insect pests. For further control, see p. 232. Fig. 38. Cantaloup Diseases. a. Soft rot, b. individual germs of soft rot (a. and 6. after Giddings), c. young cantaloup plant artificially inoculated with Mycosphasrella wilt, d. section through a perithecium of M ycosphcerella citrullina, showing immature asci, e. ascospores of M. citriiUina (c. to e. after Grossenbacher), /. Alternaria leaf blight, g. Conidiophores and spore of Macrosporium cucumcrinum (after Chester), /;. Southern blight. Family Cucurbitaceae 221 Soft Rot Caused by Bacillus melonis Gid. Soft rot is a disease which attacks the melon fruit only. The losses from this trouble often run as high as twenty-five per cent, of the crop. It is prevalent in seasons with prolonged dry weather followed by a wet spell. This results in the uneven growth and development of the fruit and hence in various crack- ings in its surface. Infection follows the place of injury, especially when the crack (fig. 38 a) occurs at a place where the cantaloupe touches the ground. The rot produced is soft with an offensive odor. The Organism. Bacillus melonis is a short rod (fig. 38 a) with rounded ends, occurring singly or in short chains of two to three, and motile by means of fiagella. It forms no endospores, no capsule, and no involution forms. It completely liquefies gelatine in fourteen days. No gas is formed, and no very dis- tinct odor is noticed. It dies by drying and exposure to light. Control. Wherever possible, irrigation should be resorted to'^in dry weather. This will encourage even growth and prevent cracking of the fruit. In wet weather spraying with Bordeaux mixture is re- commended. Occasional turning of the melons to expose them to light on all sides will also help. Dis- eased refuse should be destroyed and not be fed to stock. Downy Mildew, see Cucumber, p. 230. 222 Diseases of Truck Crops Powdery Mildew Caused by Erysiphe polygoni D. C. This disease is the same as the mildew which at- tacks garden peas, cucumbers, and numerous other hosts. Mildew is more prevalent on greenhouse melons and cucumbers than on those grown outdoors. It is characterized by powdery white patches on the leaves. The trouble is seldom serious enough in the field to warrant treatment. Mycosph^rella Wilt Caused by Mycosphcsrella citruUna (Sm.) Gr. Although this form of wilt is often a greenhouse trouble, it is nevertheless a serious disease on out- door cantaloupes and watermelons. Grossenbacher^ found that infection is localized at the nodes and not at the internodes (fig. 38 c). The injury from Red Spider or other sucking insects is perhaps responsible for opening the way to this disease. A character- istic of the trouble is that the edges of the infected areas are oily green to raisin-colored gum. The older parts of the spots are either dark and gummy or gray and dry, bearing numerous brown pycnidia. The Organism. The perithecia (fig. 38 d) are globular to inverted top-shaped, rough, dark brown I Grossenbacher, J. G., New York (Geneva) Agr. Expt. Sta. Tech. Bui. 9 : 197-229, 1909. Family Cucurbitaceac 323 to black, erumpent, and finally almost superficial. The necks of the perithecia are papillate. The ascospores are cylindrical, two-celled, hyaline, and slightly constricted at the septum (fig. 38 e). Control. Spraying with Bordeaux mixtures when the plants are about half grown and before the disease appears is recommended. Spraying should be con- tinued so that the growing parts are kept covered with the fungicide. Anthracnose, see Watermelon, p. 240. Leaf Blight Caused by Alternaria brassicce var. nigrescens Pegl. Leaf blight is a very destructive disease, often ruining entire patches which otherwise looked very promising. In some seasons, it is the greatest draw- back to successful melon culture. Symptoms. The disease begins as small round spots which gradually enlarge. These spots are dry, brown in color and made up of concentric rings or zones (fig. 38 f and g). Usually the spots are very numerous and their presence causes the leaves to curl and dry up prematurely, leaving bare vines and un- protected fruit. As a result, the melons ripen early and have an insipid taste, and are very poor shippers. Leaf blight is most serious in fields where canta- loupes are grown too long on the same field. Blight Resistant Cantaloupes. In selecting for blight resistant cantaloupe (fig. 39 a-b), we must con- 224 Diseases of Truck Crops sider (i), the yielding quality of the strain; (2), the earliness in maturing; (3), resistant qualities; (4), form, size, and netting; (5), texture and edible quali- ties; (6), shipping qualities. Blinn ^ found that resis- tance in cantaloupes seems to go hand in hand with the netting of the rind. Good netting seems also to favor good shipping melons with fine flavor. It seems that the closer the netting the better will the fruit be protected from loss of weight from evapora- tion. The Rocky Ford Pollock strain is claimed to be resistant to blight. Control by spraying, see cu- cumber, p. 232. Phyllosticta Leaf Spot Caused by Phyllosticta cucurbitacearum Sacc. This disease has not proved as serious as leaf blight. It is characterized by spots which are light in color. The pycnidia are pointed, the spores oblong and curved, hyaline and one-celled. The dis- ease may be controlled by spraying, see p. 232. Cercospora Leaf Spot Caused by Cercospora cucurbitcB E. and E. This disease behaves very much like leaf blight. In the former, however, the spots are usually of a » Blinn, P. K., Colorado Agr. Expt. Sta. Bui. 104: 3-15, 1905. Family Cucurbitaceae 225 lighter color, and are more angular in form, being limited by the veins of the leaf. The methods of control are the same as for leaf blight, see p. 223. Southern Blight Caused by Sderolium Roljsii Sacc. Southern blight, a disease that attacks a large variety of hosts, is a serious cantaloupe disease in the Southern States. The injury in most cases is con- fined to the foot of the stem, resulting in its girdling and rotting and the final dying of the affected plant. With the cantaloupe, the disease attacks the fruit, infection usually taking place at a point where it touches the ground (fig. 38 h). The disease appears first as a slight soft spot which enlarges quickly, changing the entire mass of the fruit to a mushy pulp. The exterior of the affected melon is seen to be cov- ered with a white cottony growth consisting of the mycelium of the fungus. Later there appear numer- ous whitish bodies known as sclerotia which turn yellowish and then brown. They help to carry the fungus over the winter. For methods of control, see tomato, p. 353. Root knot, see nematode, p. 49. Care in the Shipping of Cantaloupes As a rule, the greatest per cent, of the cantaloupe crop is shipped to distant markets. Growers often IS 226 Diseases of Truck Crops lose heavily from rotting of the fruit before it reaches its destination. Most of the loss may be reduced to a minimum or entirely prevented, provided growers are willing to devote more attention to certain fundamental considerations suggested by More and Branch. ^ a. Need of Quality. No one can deny the fact that products which are poorly grown, poorly har- vested, and poorly packed and shipped, are a direct loss to the grower and a serious drawback to the market. The consumer to-day insists on quality, and the grower who is to succeed cannot ignore this demand. Cantaloupes to-day are grown more ex- tensively than formerly. Competition therefore is more keen, and growers in the West are more handi- capped, because their products must travel longer distances, and therefore require more care in handling. By selecting fruit which matures early and at the same time possesses better edible and shipping qualities the difficulty will be at least partly solved. b. Care in Picking and Handling. Success in shipping depends largely on proper picking and hand- ling. With the "Netted Gem" or "Green Nets," the melons should not be harvested until completely netted. The netting should be well raised and rounded out on the surface. With immature melons the netting is flat and creased on top. For shipping short distances the melons may be picked "full slip, " i. e. just as soon as the stem separates cleanly from ^ More, C. T., and Branch, G. V., U. S. Dept. of Agr. Farm. Bui. 707 : 1-23, 1916. Family Cucurbitace^ 227 the melon, leaving a cuplike ca\'ity and tearing with it none of the rind. When shipping long distances the melons are picked on "half slip," in which case only part of the stem pulls away from the fruit, the rest breaking. It is essential that the fruit be handled carefully In the field, avoiding bruises and cuts. At the packing shed, the same care should be observed. c. Care in Packing. Good shipping also depends on careful packing. Only standard containers for shipping should be used. The crate has become the standard container for shipping melons. Crates should be made of clean, smooth, strong lumber, with all knotty and cross-grained slats discarded. Dirty and second-hand crates should not be used. Crates used in the field in harvesting should not be used for shipping. d. Need of Grading. Up-to-date growers take pains to grade their product carefully before packing. A careful grading excludes melons which are poorly netted, also known as "slickers." It is also essen- tial to exclude melons which are cracked, bruised, diseased, ill-shaped, over ripe, as well as those that are immature and those with soft stems. In pack- ing, melons of the same size and grade only should be put in the same container. e. Care in Handling. In hauling melons from the packing sheds to the car, only wagons with good springs should be used. Hauling wagons should also be provided with tarpaulin covers to protect the fruit from the sun, rain, or dust. The crates should be 228 Diseases of Truck Crops carefully unloaded into cars which are iced, if the melons are to be shipped long distances. When the cars have been properly filled, they should be dis- patched as early as possible. Freight agents should see that cars are not delayed on the road. DISEASES OF THE CUCUMBER {Cucumis sativus) Cucumbers, like cantaloupes, are subject to vari- ous diseases which render them unfit for the market or for pickling. Mosaic or "White" or "Little Pickle" Cause unknown. Mosaic has been found in Wisconsin, Michigan, Indiana, Ohio, Iowa, Illinois, Vermont, New York, Louisiana, New Jersey, Minnesota, Massachusetts, and Virginia. Symptoms. The first sign appears as a yellow mottling near the stem end of the fruit. Later the light areas are found all over the cucumber, and the darker portions frequently form protuberances. Some fruits retain their green color and show the dis- ease only by being distorted. The leaves too be- come mottled, light to dark green (fig. 40 a), and sometimes wrinkled; the stems and petioles too are dwarfed and distorted. Affected leaves die prema- turely and are replaced by others, which in turn con- V,- r.. .■%at. > f1 ' Fig. 39. Resistant Cantaloup vStraix. a. Cantaloup hill, destroyed by Alternaria leaf blight, 6. cantaloup hill resistant to Alternaria blight, a. and 6. same variety (Rockyford) growing in same field under equal conditions. Family Cucurbitaceae 229 tract the disease. The trouble is spread by insects, the principal of which is the melon louse, Aphis gossypii Glov., as well as the striped cucumber beetle, Diahrotica vittala. Satisfactory control methods are still wanting. Diseased plants should be destroyed and the field sprayed for insect pests. Bacterial Wilt Caused by Bacillus tracheiphillus Ew. Sm. The symptoms and damage caused by this wilt have already been discussed under the cantaloupe, p. 219. Recent investigations by Rand and Enlows' have shown that seeds from diseased plants^fail to reproduce wilt. This is true not only for the cucum- ber, but also for all the other cucurbit hosts which are subject to this trouble. Of the numerous varieties of cucumber and cantaloupe tested, none shows promise of resistance. While the Marblehead, Gol- den Bronze, and Boston Marrow are very susceptible varieties of the squash, the Mammoth White Bush and the Early White Bush seem to be immune to wilt. Angular Leaf Spot Caused by Pseudomonas lachrymans Sm. and Bry. This disease seems to be common on cucumbers in Florida, Michigan, and in Wisconsin. It has been ' Rand, F. V., and Enlows, E. M. A., U. S. Dept. of Agr., Jour. Agr. Research, 6 : 417-434, 19 16. 230 Diseases of Truck Crops recently studied by Smith and Bryan, ^ who described it as a new disease occurring in the Eastern and Middle-Western States. Symptoms. The trouble is characterized by angu- lar brown spots which tear or drop out when dry (fig. 40 b), giving a ragged appearance to the infected leaves. In the early stages, a bacterial exudate collects in drops on the lower surface of the spots. These exudates usually dry and become whitish. It seems that angular leaf spots attack only the foli- age but rarely the fruit. The Organism. The parasite is a short rod with rounded ends (fig. 40 c), occurring singly, or in pairs with a decided constriction; and occasionally in chains of twelve individuals or more. It is motile by means of polar flagella, produces capsules on agar and milk; no spores, and no gas is formed. The or- ganism completely liquefies gelatine in about three or four weeks. Damping off, see Pythium, p. 43. Downy Mildew Caused by Pseudoperonospora cubensis (B. and C.) Rost. Downy mildew is prevalent in New Jersey, New York, Florida, Texas, and possibly other States. It ' Smith, E. W., and Bryan, M. K., U. S. Dept. of Agr., Jour. Agr. jReiecrcA, 6: 465-476, 1915. Fig. 40. Cucumber Diseases. a. Mosaic, b. angular leaf spot (after Smith and Bryan), c. individual germs of Pseudomonas lachrymans, d. downy mildew (Manns), e. conidiophore and conidia of Phismopara cubensis, f. germinated conidia and swarm spore, g. germinated swarm spores (c to g. after Clinton), h. anthracnose. Family Cucurbitaceae 231 attacks cantaloupes, gourds, squashes, pumpkins, and watermelons. Symptoms. The disease appears as yellowish spots on the leaves, which have no definite outline (fig. 40 d). With warm moist weather, numerous spots coalesce, and soon the affected leaves turn yellow and die. With cool weather the spots seem to spread less rapidly. The disease appears to work on the older leaves, beginning on those on the center of the hill and working outward. With infected plants the center of the hill is clearly marked by a cluster of yellow leaves. Diseased plants may flower pro- fusely, but no fruit is produced. The few cucumbers which set are small, deformed, and unfit for the market. Downy mildew is most prevalent in August with moderate rainfall and hot weather. The disease spreads very rapidly and a large cucumber field may be a total loss in less than from eight to ten days. The Organism. The fungus derives its food from the host cells by means of suckers or haustoria. The mycelium is hyaline, non-septate ; the conidiophores (fig. 40 e) arise in small clusters through the leaf stomata and are branched and flexuous. The zoosporangia are hyaline but slightly violet, tinted in mass. Germination of zoosporangia is by means of motile zoospores (fig. 40 f-g) . The oospore, or sexual fruiting stage, was first found on the host by Ros- tovtsev. Downy mildew may be kept in check by spraying with Bordeaux mixture. 232 Diseases of Truck Crops Powdery Mildew Caused by Erysiphe cichoracearum D. C. Powdery mildew of cucumbers is not a serious trouble, since it usually attacks plants which have somewhat passed their usefulness. Like all powdery mildews, the causative fungus grows on the surface of the leaf, giving it a white mealy appearance. From the mycelium are produced erect threads which bear the summer spores of the fungus. According to Humphrey, ' the ascus or winter stage appears as minute dark-brown rounded capsules enclosing a group of spore sacs within which are formed the ascospores. Anthracnose (fig. 40 h), see Watermelon, p. 240. Root Knot, see Squash, p. 237. Spraying Cantaloupes and Cucumbers Cantaloupes and cucumbers cannot always be grown profitably unless the crops are sprayed. It is fortunate that most of the foliage and fruit diseases may be kept in check by spraying with Bordeaux mixture. The work of Orton^ and others has shown that not only does spraying control the various dis- eases, but viewed from the point of view of dollars and cents it undoubtably pays. ' Humphrey, J. E., Massachusetts Agr. Expt. Sta. loth Ann. Rept.: 225-226, 1892. ^ Orton, W. A., U. S. Dept. of Agr. Farm. Bui. 231 : 5-24, 1905. Family Cucurbitaccae 233 Cuctimbers grown for pickles, however, should not be sprayed, as spraying reduces the number of fruit, although it is so beneficial for fruit which are to be left to grow to market size. For an area less than one acre, a small hand pump sprayer, or preferably a good small compressed-air sprayer will answer the purpose. For fields of one to five acres a barrel sprayer is recommended. For fields above five acres or more, a good power sprayer must be able to apply at least one hundred gallons per acre. To do thorough spraying, a slow walking team should be chosen, but the pump should be geared correspondingly high so as to maintain full pressure at a low speed. The strength of Bordeaux recommended by Orton as safe from burning is a 3-6-50 formula. From the writer's experience, he would not advise using formu- las stronger than this, especially under Southern climatic conditions. The time to spray first is when the vines begin to run. The number of succeeding applications should be governed by climatic condi- tions. In damp warm weather, spraying should be re- peated every second or third week. The object is to keep all growing parts of the plant thoroughly covered with the fungicide. For further directions on spraying and the preparations of the ingredients, see p. 361. In some seasons, the melon louse, Aphis gossypii, causes great damage to cantaloupes and cucumbers. The pest sucks the life of the plant by feeding on its juices. Durst ^ recommends spraying with "Black ' Durst, C. E., Illinois Agr. Expt. Sta. Bui. 174 : 321-334, 1914. 234 Diseases of Truck Crops Leaf 40," used at the rate of one part to one thousand of water. This will control the aphids. "Black Leaf 40" readily mixes with Bordeaux mixture. To control both fungus and plant lice, add to every one hundred gallons of Bordeaux one pint of "Black Leaf 40." To control chewing insects, such as the cucumber striped beetle or caterpillars feeding on the plants, add to each one hundred gallons of Bor- deaux three pounds of powdered arsenate of lead. DISEASES OF THE CITRON {Citrullus vulgaris) Citrons are not grown commercially. They are found as weeds in melon patches or anywhere in the farm where permitted. The citron is a very hardy plant, and it is subject to but few diseases. Anthracnose, see Watermelon, p. 240. Leaf Spot, see Watermelon, p. 243. Gourd Disease, see Squash, p. 234. MusKMELON Diseases, see Cantaloupes, p. 219. Pumpkin Diseases, see Squash, p. 234. DISEASES OF THE SQUASH (Cucurbita maxima, C. pepo, and C. Moschata) Squashes, with but few exceptions, are subject to the same diseases as affect the cantaloupe and the cu- cumber. Squashes are usually grown for local mar- kets, and because of their diseases in many places their culture has been abandoned. Bacterial Wilt, see Cucumber, p. 229. Fig. 41. Squash Diseases. a. Showing squash blossoms invaded by the fungus Choanophora cucurbitarum, b. squash entirely rotted by the Choanophora fungus, c. young conidiophore of Choanophora with ramuli developing on the primary vesicle, d. mature capitulum covered with a layer of conidia, e. conidia, /. sporangia and columella, g. sporangio spores with tufts of hair-like appendages, h. mature zygospore («, c. to /;. after Wolf), i. Pusarium wilt of young squash plants, ./. Rhizopus rot. Family Cucurbitaceae 235 Fruit Rot Caused by Choanophora cucurbitarum (B. and Rav.) Thax. Fruit rot is a common disease of the summer squashes. It has been found in North and South Carohna, Massachusetts, New York, Ohio, Michigan, Connecticut, Florida, and Texas. The disease is of Httle importance in dry seasons. It is, however, favored by conditions of high humidity and excessive rainfall, or by heavy dews at night. Symptoms. It usually attacks the flowers, or especially the remnants, of the old calyx (fig. 41 a). The latter when affected become shriveled and cov- ered with a thick crop of brown conidiophores of the causative fungus. From the floral parts, the my- celium works downward and into the young squash, which wilts very rapidly, turning into a soft rot and later covered by a gray growth of conidiophores (fig. 41 b). As far as is known, the fungus does not attack any other part of the squash plant except the floral parts and the fruit. The varieties of squash most affected by fruit rot are the "patty pan" types, commonly known as cymblings. Wolf^ has found Choanophora cucurbi- tarum on fading flov/ers of cucumber, Althea, scarlet hibiscus, okra, and cotton. The Fungus. The conidiophores when young are whitish, but at maturity take on a metallic luster. ' Wolf, F. A., U. S. Dept. of Agr., Jour. Agr. Research, 8 : 319-328, 1917- 236 Diseases of Truck Crops The top end is broadest, becoming dilated into a caputate vesicle. From this head are produced from a few to a dozen small branches, the tips of each in turn becoming vesicular (fig. 41 c). Each vesicle now becomes covered with a dense layer of conidia (fig. 41 d). The latter are light to reddish brown in color (fig. 41 e). The conidia germinate by means of a germ tube. Sporangia are formed in pure culture but not on the host. Sporangia are first evident as white pendant enlargements, becoming separated from the sporangiophore by a globular columella (fig. 41 f). Mature sporangiospores are larger than the conidia, are smooth, and possess terminal hyaline appendages (fig. 41 g). The spores germinate by means of the germ tube, as is the case with the conidia. Chlamydospores are not uncom- mon and they have often been observed during the winter. The formation of zygospores is a common occurrence on culture media, but not on the host. The method of zygospore formation and germina- tion has not as yet been definitely worked out. Control. The spores of Choanophora cucurhitarum are undoubtedly carried from flower to flower by insects. Spraying, as outlined for cucumbers, is also recommended for the squash, p. 232. Soft Rot Caused by Rhizopus nigricans Ehr. Soft rot very often cannot be distinguished from the fruit rot above mentioned (fig. 41 j). The symp- Family Cucurbitaceae 2^] toms in both diseases are very much aHke. The only disparity consists in the difference of the two causa- tive organisms. For a further study of Rhizopus nigricans, see soft and ring rot of the sweet potato, pp. 156-159- Powdery Mildew, see Cucumber, p. 232. Anthracnose, see Watermelon, p. 240. Leaf Spot, see Cantaloupe, p. 224. Wilt or Yellows Caused by Fusarium cucurbitcB Taub. ^ One of the greatest drawbacks to squash culture in many of the Southern States, especially in Texas, is a disease known as wilt (fig. 41 i) or yellows. The symptoms of the squash wilt are identical with those of the watermelon wilt, see p. 244. However, the organ- ism F. cucurbitcB is different and distinct from the three species of Fusarium which are capable of producing a wilt on watermelon. The name Fusarium cucurbi- tcB n. sp. is therefore given to the squash wilt organism to distinguish it from other species of Fusa- rium. From investigations by the writer there has been found no variety which is resistant to wilt. On the other hand, the pumpkin Cucurbita pepo, and the "sugar through" gourd Lagenaria vulgaris will thrive in soils where squashes are known to fail from wilt. Watermelons, cowpeas, cotton, and okra will also thrive well in Fusarium-sick soil of squashes. Occasionally it is found that cowpeas and okra will ' From unpublished data of the author. 238 Diseases of Truck Crops die from a wilt in the same field where squashes are not thriving. However, the writer has been able to prove that the wilt of cowpea and okra are diseases caused by two distinct species of Fusarium, and that both of these parasites may be found in the same field also infected with Fusarium cucurbitce of the squash. Root Rot, see Rhizoctonia, p. 45. Root Knot, see Nematode, p. 49. DISEASES OP THE WATERMELON {CUrullus vulgaris) Malnutrition Cause, physiological. Malnutrition seems to occur in fields deficient in potash. The trouble is apparently new, brought about by the scarcity of potash, due to war conditions. The disease is characterized by Ught brown spots located around the veins and margins of the leaf. The disease must be further investigated before re- medial measures may be suggested. Bacterial Wilt, see Cantaloupe, p. 219. Downy Mildew, see Cucumber, p. 230. Powdery Mildew, see Cucumber, p. 222. Honey Dew or Sooty Mold Caused by Capnodium sp. Watermelon stems, petioles, and leaves often be- come coated with a black sooty growth. This is JiT^ Fig. 42. Watermelon Diseases. a. Stem end rot (after Meier), 6. anthracnose of foliage, c. anthracnose on fruit, d. Fusarium wilt of young seedlings, e. blossom end rot. Family Cucurbitaccae 239 more abundant on the older leaves, or even on the nearly mature melon fruit. Although the mold seems to grow superficially on the outside of the affected parts, the result is a general suffocation, since sun- light and free circulation of air are interfered with. Sooty mold undoubtedly grows on the sweetish ex- creta of plant lice, and is severest during seasons of Aphis epidemics. Spraying with "Black Leaf 40" to control Aphis gossypii will also control sooty mold. The fungus Capnodium apparently does not derive any nourishment from the watermelon, but from the honey excreted by plant lice. Mycosphaerella Wilt, see Cantaloupe, p. 222. Stem End Rot Caused by Diplodia tubericola (E. and E.) Taub. This disease was first studied by Meier ^ who found the trouble confined mostly to watermelons in transit. Many carloads when reaching their destination showed a loss from it of 75% to 95%. Symptoms. The first indication of the rot is a browning and shriveling of the stem end of the fruit (fig. 42 a). Rotting begins at the point of attach- ment of the melon to the stem of the plant. The flesh of the affected melon blackens, softens, and becomes watersoaked and then slimy. Such melons when left to themselves become black, wrinkled, and mummified. Infection undoubtedly must take place ' Meier, F.C., U.S. Dept. of Agr., Journal ofAgr. Research, 6 : 149- 152, 1916. 240 Diseases of Truck Crops in the field before loading. The disease incubates while in transit and makes its appearance when the assigned shipment reaches its final destina- tion. The Organism. The organism which causes stem end rot of watermelon is the same which is re- sponsible for the Java black rot of the sweet potato. This has been proved by Meier and by the writer. For further discussion of the fungus, see p. 165. Control. Diplodia tuhericola may easily live over from year to year on the cull melons left in the field, on the sweet potato refuse or on any other trash. Therefore infected culls and refuse should be de- stroyed. In hauling melons to the car, only wagons with springs should be used. The cars should be carefully swept and cleaned before loading. Rough handling or bruising should be avoided as much as possible and only sound melons should be loaded in the car. The fruit should be carefully packed so as to avoid bruising from shaking when the cars are moved. Anthracnose Caused by Colletotrichum lagenarium (Pass.) E. andH. Anthracnose is a disease the seriousness of which depends on weather conditions, it thriving best dur- ing hot, moist weather. It is very prevalent in many mt: *. ..ijr*^^ * Fig. 43. Watermelon Anthracnose. a. Healthy watermelon hill, b. field destroyed by anthracnose. Family Cucurbitaceae 241 States, although it has not as yet been found to be serious in Texas. Symptoms. It attacks all parts of the plant except the root. On the stems it causes watersoaked spots, which in time turn brownish and become depressed and cracked. On the leaves, somewhat circular dark spots become so numerous as to involve the entire area (fig. 42 b), resulting in the death of the leaf. Diseased leaves soon crinkle, turn black, and have the appearance of being burned by fire. On the fruit, anthracnose is manifested on the rind as cir- cular deep depressions (fig. 42 c) which soon become covered with a salmon-colored coat made up of the spores of the fungus. Ordinarily the spots do not go deeper than the rind. Under improper methods of shipping,, the fungus eats into and penetrates the flesh of the melon which decays rapidly. Anthrac- nose reduces the market value of the melons, and makes shipping a very risky affair, since the disease readily spreads in the car. This is especially true when the cars are sidetracked and held too long in transit. In the field, anthracnose may ruin the entire stand (fig. 43 a-b). Besides attacking watermelons, anthracnose also attacks cucumbers, cantaloupes, citrons, and gourds. The disease is not usually serious on new land; but on land where watermelons have been grown in suc- cession for a period of years, or where melons fol- lowed cantaloupes or cucumbers, the disease may become serious. The Organism. In structure, Colletotrichum lage- 16 242 Diseases of Truck Crops narium resembles the organism of bean anthracnose, see p. 263. The watermelon fungus has a peculiar ability to remain dormant during dry weather; but it is easily revived by rains or dew. This is why anthracnose often appears overnight in carloads shipped to market. The fruits of the fungus are borne in masses on the pustules which take on a salmon color. The spores are typical of all CoUeto- trichums — that is, oval, one-celled, and hyaline. The setae in C. lagenarium are not very plentiful. In pure culture it resembles C. lindemuthianum; how- ever, pathologically it is distinct from the latter, since numerous attempts by the writer and by others have failed to infect growing bean plants with the watermelon anthracnose or the watermelon with that of the bean. Control. With this disease, prevention is, of course, the cheapest method of control. From what has been said, it is evident that it is never wise to grow watermelons too long on the same land. In prevent- ing the disease from gaining a foothold on the land, a three-year rotation will probably answer the pur- pose. On lands in which the crop has suffered severely from anthracnose, a longer rotation, say six years, may be necessary. The disease is carried over in the soil from year to year on the dead leaves, vines, and diseased fruits which remain in the field. These, therefore, should never be plowed, but destroyed by fire. Spraying, too, will help to keep the disease in check. Bordeaux in this case is the standard fungicide to use. However, it should be borne in Family Cucurbitaceae 243 mind that watermelon leaves are very tender and hence susceptible to injury. Recent experiments by the writer have shown that a very weak Bordeaux with a large excess of lime should be used in order to prevent the burning of the foliage. Where this pre- caution is overlooked, a greater injury will result from the use of the fungicide than from the disease itself (fig. 44 b). A Bordeaiix made up of three pounds of copper sulphate, eight pounds of lime, and fifty gallons of water, to which is added one pound of powdered arsenate of lead, will answer the purpose well. The lead arsenate in this case is used against various caterpillars which often feed on the leaves of the plants. Paris green should not be used because of its tendency to bum the foliage. Cercospora Leaf Spot, see Cantaloupe, p. 224. Cercospora Leaf Spot Caused by Cercospora citrulUna Cke. This form of leaf spot is induced by a species of Cercospora different from that which attacks canta- loupes. The trouble usually appears on the oldest leaves as circular spots bordered by a dark brown or purplish zone beyond which is an area of yellow. The mature spots have gray centers. This form of leaf spot is prevalent on watermelons in Texas. It may be controlled by spraying in the same way as recommended for anthracnose. 244 Diseases of Truck Crops Vine Wilt or Yellows Caused by Fusarium niveum Ew. Sm.; Fusarium citrulli Taub.^; Fusarium Poolensis Taub.' Failure of the watermelon crop in many of the Southern States may be safely attributed to wilt. There is no other watermelon disease that is so diffi- cult to control. The reason is obvious. The causa- tive fungi live in the soil as semi-saprophytes. The longer watermelons are grown on that soil, the worse the disease becomes. In severe cases the crop may be a total failure, or the loss run as high as fifty per cent, of the crop. Symptoms. There is no outside spotting nor are there any lesions to indicate the presence of wilt. The source of the trouble is confined entirely to the interior of the roots and stems. The leaves of an affected plant suddenly droop; this is followed by a rapid wilting of all the vines in that hill (fig. 44 a) from which they never revive. The wilting is more intensified during a warm dry spell. Occasionally only one or two vines in the hill wilt and die while others in the same hill remain alive for some time before succumbing to the disease. In pulling out a plant that has recently died, its roots are found to be sound with the exception of a dull yellowish color which the exterior exhibits. In splitting open a vine ' From unpublished data by the writer, the organism was carried as Fusarium No. 106. ^ The organism was carried as Fusarium No. 1 16. '''sXtj?: Fig. 44. Watermelon Diseases. o. Wilt {Fusan'um niveum). b. Bordeaux injury, c. Tom Watson, an ideal shipping melon, d. macroconidia of Fusarium niveum. Family Cucurbitaceae 245 or root of the diseased plant, its interior fibrovascular bundles will be browned. The browning indicates the presence of the parasite. Wilt is not always confined to the older plants. In badly infected fields young seedlings begin to die at an early age (fig. 42 d), resulting in a very poor stand. From the investigations of the writer, it has been found that Fusarium citrulli is more active on seedlings than are the other two species of Fusarium. This, however, is not intended to convey the idea that F. niveum and F. Poolensis are not capable of pro- ducing wilt on the younger seedlings. The Organisms. The three species of Fusarium which produce wilt of watermelon may be readily distinguished when grown in flasks on commeal. Fusarium citrulli is entirely different from the two others in that it forms a glistening, flat, compact, flesh-colored dry growth confined to the surface of the cornmeal. Growth is slow, and no color is pro- duced in the substratum for a considerable time, about two months or more. Fusarium Poolensis at first greatly resembles F. niveum in growth and in color. Later, however, F. Poolensis takes on a deep blue to almost indigo which is retained indefinitely. The three species of Fusarium have been definitely proved by the writer to be the cause of the water- melon wilt. Infection can take place only on water- melons and not on any other cucurbit hosts, nor on cotton, okra, or cowpea, the wilts on all of which are caused by different species of Fusarium. It is possible, however, that a sick watermelon field may also be 246 Diseases of Truck Crops infected with Fusarium cucurbitce, thus making it also sick to squashes. Control. Since the disease works in the interior of the plant, it is obvious that spraying would be of little help. Rotation of crops is the only practical method of control. It usually takes from two to three years for wilt to establish itself very seriously in the field. Because of this, growers often fail to appreciate its importance until too late. Any possible profits made during the time the crop has been grown in succession on the same land are more than offset by the fact that the infected soil is ren- dered sick and unfit for watermelons for ten years or longer. Watermelon plants suffering from wilt should never be plowed under, but should be pulled out, dried, and burned. Wilt may be spread by cattle and horses which are allowed to pasture in the sick melon patches, and then brought to healthy fields. Finally a method which promises great re- lief is the development of resistant varieties which are able to grow in sick soils. The United States Department of Agriculture has developed a wilt re- sistant variety named Conqueror. This is a cross between the citron and the Eden. The Conqueror, however, is not as yet popular with the market be- cause of the uncertain qualities of the citron which it still has. Resistant varieties may no doubt be ob- tained by selection with the best commercial vari- eties. For methods of selection for resistance see P- 374- Root Knot, see Nematode, p. 49. Family Cucurbitaceae 247 Fruit Rot Caused by Sclerotium Roljsii Sacc. This form of rot is seldom serious enough to war- rant any treatment. The fungus does not seem to find the watermelon fruit as suitable a host as the cantaloupe. On watermelons, rotting starts at a bruise and at points where the melon touches the ground. Decay is slow and is always indicated by a cottony growth at the rotted area. Blossom End Rot Cause : probably due to fungi. This is a disease which attacks the blossom end of the fruit (fig. 42 e) and causes a dry rot, but which does not usually penetrate very deep. Nevertheless, affected melons are unfit for the market, although they ripen earlier and have a much sweeter taste. The cause of this trouble is as yet unknown. How- ever, numerous observations seem to indicate that with at least one form of blossom end rot it seems to be brought about by a dry spell and a lack of mois- ture in the soil. This is especially the case in fields where coarse manure is used instead of good compost. In dry seasons, the coarse manure fails to decompose properly and, at the same time, dries, and hence re- sults in injury to the fruit. To prevent this, so far as possible, only well rotted manure should be 248 Diseases of Truck Crops used. If the coarser manure has to be used, care should be taken to apply it from four to eight weeks before planting, thus giving it ample time to decom- pose. To have the greatest effect, manure should be applied as deep in the furrows as possible, since the tap-root grows very deep in the soil. It should be remembered that the watermelon plant has numer- ous long secondary roots which are heavy feeders and which do not benefit from manure if it is applied in the center of the hill. Such superficial application, therefore, often results in starved plants, which be- come further weakened by spells of dry weather, or by other unfavorable conditions. To obviate this condition, some chemical fertilizer should be applied broadcast. The amount of manure necessary for one acre is about seven tons, applied at the rate of one good forkful to each hill. In connection with this, about four hundred pounds of well balanced fertilizer should also be worked in. In very dry seasons, small amounts of nitrate of soda, applied broadcast, will decidedly benefit the plants. The aim in fertilizing should be to supply sufficient humus to the soil, thus also taking care of the soil moisture at a time when the plant needs it most. Moreover, the use of proper food supply will result in more vigorous plants, with an abundance of foliage protect- ing the plants from burning and, at the same time, reducing blossom end rot. There are other forms of blossom end rots. Some may possibly be attributed to imperfect fertilization or weak pollen, while others are undoubtedly caused Family Cucurbitaceae 249 by parasitic bacteria and fungi. However, without further knowledge it is impossible to suggest other methods of control. The best shipping melon is the Tom Watson (fig. 44 c). This melon, however, is no less susceptible to diseases than any other variety grown under similar field conditions. WEEDS The wild cucumber Micrampelis (or Echinveyster) lobate is subject to cucumber mosaic and to bacte- rial wilt. With this exception no cucurbit weeds are subject to the diseases which attack the cultivated species. CHAPTER XV FAMILY GRAMINE.E Of this great family the only crop that concerns the trucker and gardener is sweet com. This is grown to a great extent in the more northern States. In the South, the ordinary field com is grown instead of sweet corn and is sold for "roasting ears " or on the cob in the milky stage. The present discussion will limit itself to sweet com only. It is estimated in the Thirteenth United States Census that the total area of sweet com in the United States in 1909 was 178,224 acres and the crop was valued at $2,719,340. The States ranked according to area in sweet corn were: New York, Illinois, Maryland, Ohio, Iowa, Pennsylvania, New Jersey, Maine, Indiana, Michi- gan, Massachusetts, Wisconsin, Kansas, Nebraska, Missouri, California, Minnesota, Virginia, Connecti- cut, Delaware, Louisiana, Vermont, and Kentucky. States with less than one thousand acres are omitted. DISEASES OF THE SWEET CORN {Zea Mays) Although corn is considered a hardy plant, it is nevertheless subject to numerous diseases. Of the 250 Fig. 45. Sweet Corn Diseases. a. Bacterial blight, b. individual blight organisms (a. to b. after F. C. Stewart), c. smut, d. smut spores, c. and/, germinating spores of jjstilago zece{d. to/, after J. B. S. Norton). Family Gramineae 251 sweet com but three diseases need concern the trucker. Bacterial Wilt Caused by Pseudomonas Stewarti Erw. Sm. Bacterial wilt is perhaps one of the most serious diseases of sweet corn. The trouble is very prevalent in Long Island, New York, where it was first studied by Stewart.^ It is also prevalent in New Jerse}^ Maryland, West Virginia, Ohio, Iowa, Illinois, and probably many other States. Symptoms. Bacterial wilt has been carefully studied by Dr. Erwin F. Smith, ^ who finds that the symptoms of this disease are very distinctive. The first mark on good sized plants is a drying out and whitening of the tassel, giving the top of the plant a peculiar whitish appearance. Another sign is a dwarfing of the plant, followed by a drying of the basal leaves which gradually works upwards (fig. 45 a) . The affected leaf dies from the tip downwards or from the margin inwards. The disease often attacks young plants and even seedlings, in which case they dry and die out at an early stage. If an infected plant is cut across the stem, we find a yellow slime oozing out from the bundles; this slime is teeming with the bacteria. In cutting through a ' Stewart, P. G., New York (Geneva) Agr. Expt. Sta. Bui. 130 : 424-439, 1897. ^ Smith, E. P., Bacteria in Relation to Plant Disease, 3 : 89-174, Washington, D. C. 252 Diseases of Truck Crops stem longitudinally, it will be found that the bundles from which the yellow slime oozes out are browned or bright yellow. This shows that the germ is con- fined to the fibrovascular bundles of the stem and leaves. The Organism. Pseudomonas Stewarti is a short rod with rounded ends (fig. 45 b). It occurs singly, in pairs, or fours, and moves about by means of polar flagella. It grows slowly on gelatine without lique- faction. On agar plates it grows slowly, forming small round colonies. It produces no gas and is strictly aerobic ; the organism is very sensitive to light. Control. It is likely that the disease is carried with the seed. Hence the latter should be secured from localities free from wilt. Before planting, seed should be disinfected in formaldehyde, see p. 99. Not all varieties of sweet corn are equally subject to wilt; hence truckers are advised to try to develop a resistant strain or strains of commercial varieties. On the methods of selection for resistance, see p. 374. Finally, fields badly infected should be rotated and devoted to other crops for about three to four years. As far as is known the disease only attacks com, so other cereals may be used in the system of ro- tation. Smut Caused by Ustilago zea. (Beck.) Ung. Corn smut is different from any smut which at- tacks other cereals. The greatest damage is experi- Family Gramineae 253 enced when the disease attacks the ear, destroying or rendering it useless for market purposes. Symptoms. Corn smut does not usually make its appearance before the plants are about three or four feet high. It is manifested as boils which may attack any part of the leaves (fig. 45 c) , stalks, tassels, or ears. The boils are whitish to glossy, then purple, finally rupturing and liberating a black powdery mass of the spores (chlamydospores) of the fungus. The Organism. Within the tissue of the affected host the smut mycelium consists of short slender branched filaments closely interwoven. These slender filaments swell, gelatinize, and portions of them round off as spores. The latter retain their vitality for more than one year. The chlamydo- spores (fig. 45 d) germinate by sending out a tube which in turn bears true conidia (fig. 45 e, f). The latter germinate by sending out a tube which pene- trates the host. Control. Com smut is not carried with the seed as is the case with oat or wheat smut. Seed treat- ment in this case will therefore be useless. The dis- ease is carried with the manure or in the soil. The best remedy, therefore, is to cut out and destroy by fire all smut boils as they appear. This must be done before the boils are ruptured. If this is care- fully practiced by everyone in each community corn smut will soon disappear. Smutted ears or stover should never be fed to animals, as this is a common way of infecting the manure pile. 254 Diseases of Truck Crops Rust Caused by Puccinia sorghi Schw. Corn rust is a disease which is of restricted dis- tribution and which is never serious enough to war- rant treatment. It is characterized by chocolate colored pustules on the leaves and leaf sheaths. The secidium of this rust occurs on oxalis and is known as JEcidium oxalidis Thiim. The uredo and puccinia stages both occur on the com . WEEDS So far as is known, none of the Graminaceous weeds are subject to the three diseases of the sweet corn here mentioned. Nevertheless, weeds should never be tolerated. CHAPTER XVI FAMILY LABIATE This family contains numerous plants which are of very slight economic importance. If grown at all, they are cultivated on a very small scale, and sold for condiments. Many of them are tropical or semi-tropical, but most of them could be grown in frames or indoors. The following is a list of plants which belong to the Labiatas: Balm, catnip, clary, horehound, hyssop, lavender, mint, peppermint, pennyroyal, rosemary, sage, spearmint, summer savory, sweet basil, and sweet marjoram. Of all these hosts, peppermint and spearmint alone are extensively grown in the United States. The vola- tile oil distilled from these plants is the principal marketable product, although there is also a limited demand for the dried herb, especially the spearmint, which is used as a culinary herb for flavoring sauces and cooling drinks. Of recent years, these herbs have come into extensive use for flavoring chewing gum and confectionery. The United States, Japan, Russia, Germany, and England produce all of the peppermint and spearmint oils. Fleet ' has estimated • Fleet, W, v., U. S. Dept. of Agr. Farm. Bui. 694 : 1-12, 1915. 255 256 Diseases of Truck Crops the total annual production of these oils to be 600,000 pounds, 250,000 of which are produced in the United States. Peppermint and spearmint are grown in Wayne County, New York, and in a few northern counties of Ohio, Maryland, and Indiana. Accord- ing to the Thirteenth Census of the United States the 1909 area devoted to mint in America was es- timated at 8,195 acres. The total crop was valued at $253,000. Of the States growing most on a com- mercial scale may be mentioned Indiana, Michigan, New York, and Tennessee. DISEASES OF THE BALM {Melissa officinalis) Rust Caused by Puccinia menthcB Pers. The disease attacks about thirty-five members of the mint family. All the three stages i. e., aecidio- spores, uredospores, and teleutospores, occur on the same host. The disease is characterized by brown sori which are at first cinnamon colored and later chestnut brown. Diseased leaves curl and dry up. The disease is not sufficiently important to warrant treatment. Leaf Spot Caused by Septoria melisscB Desm. The disease is characterized by numerous brownish spots which are angular and apparently limited by the Family Labiatae ^257 veins of the leaves. Leaf spot has not been found in the United States, but it is said to be common in Europe. DISEASES OF THE CATNIP {Nepeta cataria) Stem Rot Caused by Didymella cataricB (C. and E.) Sacc. This trouble causes spots on the stems. The disease was first found in New Jersey, but it is of little importance. Leaf Spot Caused by Septoria nepetcE E. and E. Leaf spot is characterized by purplish brown cir- cular spots which are surrounded by a band of deeper brown. The disease was first found in Racine, Wis- consin, and is apparently prevalent on the Canadian- American border. Stem Rot Caused by Diplodinia herbicola (B. and C.) Sacc. Stem rot was first reported from Pennsylvania, but it is of no economic importance. 17 258 Diseases of Truck Crops DISEASES OF THE HOREHOUND {Marrubium vulgare) Powdery Mildew Caused by Erysiphe galeopsidis D. C. Powdery mildew is characterized by powdery white patches on the leaves and stems. The trouble is not known to occur in the United States. Leaf Spot Caused by Diplodia herbarum (Corda) Lev. The spots are roundish to irregular, numerous, brownish to dark in color. The disease attacks the older leaves, causing them to drop off prematurely. DISEASE OF THE MINT Rust, see Balm, p. 256. DISEASE OF THE PEPPERMINT {Mentha pepenta) Peppermint is a very hardy plant. With the ex- ception of Rust (see Balm, p. 256), it is practically free from attacks of fungus diseases. The same is also true for the spearmint, Mentha viridis, which is known to be attacked by the same rust diseases as the balm and all the other Labiatse. As far as we know the weeds in this family are not carriers of diseases which concern the trucker. CHAPTER XVII FAMILY LEGUMINOS^ This important family includes crops which are greatly valued by the consumer. Of the numerous legume plants, we will consider only those which concern the trucker, — viz., bean, lima bean, cowpea, and the garden pea. According to the Thirteenth Census of the United States, the total area devoted to dry edible beans in the United States in 1909 was estimated at 802,991 acres, and the total crop valued at $21,771,482. That of green beans was 53,610 acres, the total crop valued at $2,844,951. The important leading bean States are Michigan, California, New York, New Mexico, Kentucky'-, and Maine. The estimated area in dry peas in 1909 was 1,305,099 acres, and the total crop valued at $10,963,739; while the area for green peas was 70,487 acres, yielding a crop valued at $2,785,502. The States ranked according to largest area devoted to peas ' were as follows : South Carolina, Georgia, North Carolina, Michigan, Alabama, Wis- consin, Mississippi, Arkansas, Texas, Illinois, Tennes- ^ In the Thirteenth Census, no distinction is made between the garden pea and the cowpea. 259 26o Diseases of Truck Crops see, Louisiana, Colorado, Missouri, Indiana, Virginia, Kentucky, Florida, and Oklahoma. DISEASES OF THE BEAN {Phaseolus vulgaris) Bean growers annually lose heavily from various bean diseases. There is no other truck crop, potatoes excepted, which has received as much attention from plant pathologists as the bean. With our present knowledge, many of the diseases may be controlled. Blight Caused by Pseudomonas phaseoli Ew. Sm. Symptoms. If the weather is wet during planting time, the seed may rot in the ground and never germi- nate. At other times the root of the young seed- lings may decay and the result will be a very poor and uneven stand. In dry weather a better germi- nation is obtained, but the disease works on the older plants in irregular spots in the field. Due to the lack of a normal root system, the affected plants are yellowed and wilted at daytime, but they slowly revive at night. Should the weather become muggy in midsummer, infected fields appear as though they were drenched with hot grease, the leaves having a burned appearance (fig. 46 a) . As a result, the injured plants seem to make a desperate attempt to produce new foliage which in turn becomes affected, hence the pods cease filling and ripening is very uneven. In carefully examining diseased seed, it is found to be yellowed and shriveled ; or, in light cases of attack, Fig. 46. Bean Diseases. a. Bacteriosis on leaf, 6. bacteriosis on pods. c. individual germs of bacteriosis (after Smith), d. bean plant killed by streak (,/?. to d. after Sackett), e. streak on pods. Family Leguminosse 261 there are found indefinite yellow spots or blotches. On the leaves the trouble appears as watersoaked spots which later are amber colored (fig. 46 a). On the stems and pods (fig. 46 b) a canker is formed which somewhat resembles the canker produced by Colletotrichum lindemuthianum. From the stem the disease works down to the main root, causing it to rot. The Organism. Pseudomonas phaseoli is a short rod rounded at both ends, motile by means of polar flagella. It liquefies gelatin slowly, coagulates milk, and the whey separates slowly with acidity. 4 Control. The same as for anthracnose, p. 265. Streak Cause, Bacterial. Streak is a disease which is little known. It has been recently studied by Sackett, ' although the cause has not been definitely determined. The trouble may perhaps be the same as the streak of the sweet pea, caused by Bacillus lathyri Manns and Taub. Streak attacks stems, leaves, and pods (fig. 46 d,e) of the bean plant. On the pod and on the leaves the disease appears as peculiar rusty to orange brown spattered spots which run down in streaks. Dis- eased foliage drops off prematurely, giving the plant a denuded appearance. For methods of control, see bean anthracnose, p. 265. Damping Off, see Pythium, p. 43. Downy Mildew, see Lima Bean, p. 267. ' Sackett, W. A., Colorado Agr. Expt. Sta. Bui. 226 : 27, 1917. 262 Diseases of Truck Crops Rust Caused by Uromyces appendiculatus (P.) L. Rust is seldom serious enough to warrant treat- ment. The disease attacks all parts of the bean plant except the roots. On the foliage, it appears as little brown pimples or son (fig. 47 a) the size of a pin's head. These pimples soon appear on the pods (fig. 47 b), petioles, and stems, being more numerous however on the leaves and pods. The pimples as they get older turn from brown to black in color. The powder discharged from the sori is made up of countless numbers of the fungus spores. Rust does not live over on the seed, but rather on the dead re- fuse of the bean plants. Bean rust has the aecidio- spores, uredospores (fig. 47 d), and teleutospores (fig. 47 c) on the same host. Clean culture, burning of trash and dead plants, and selection of resistant strains or varieties is re- commended. Powdery Mildew Caused by Erysiphe polygomi D. C. Powdery mildew is serious on fall beans in many of the Southern States, and on beans grown for the early market. It is characterized by white, mealy patches on the surface of the leaves and stems. The foliage soon turns yellow and dry. Powdery mildew may be controlled by dusting the plants with flowers of sul- ^ ^ ^C .,"• • Fig. 47. Bean Diseases. a. and 6. Rust on leaf and pods. c. section through bean leaf showing bean rust, summer spores, d. section through bean leaf, showing bean rust, wmter spores f. anthracnose, /. section through bean seed, showing relation of anthracnose to the host (f. d. and/, after Whetzel), g. Cercospora leaf spot, h. Isariopsis ^riseola leat spot, i. conidiophores and conidia of Isariopsis. Family Leguminoss 263 phur, or by spraying with potassium sulphide at the rate of three ounces of the chemical dissolved in ten gallons of water. SCLEROTINIA ROT Caused by Sclerotinia liber tiana Fckl. Sclerotinia rot is a disease which attacks fall snap beans. The trouble is prevalent in Norfolk, Virginia, where it has been studied by McClintock. * During a period of hot humid weather in September the disease may suddenly break out in great severity. Usually withering and decaying of stems and pods where the plants are thickest is the first symptom that attracts attention (fig. 51 c). On closely examining infected stems and pods, we find that they are water- soaked, and overrun by the white mycelial growth on which appear numerous hard, black sclerotia. In the field, the Black Valentine snap bean seems to be more resistant to rot. For a description of the causative fungus and methods of control, see lettuce drop, p. 143. Anthracnose Caused by Colletotrichum lindemuthianum (Sacc. & Magn.) B. and C. Anthracnose may be considered one of the most destructive bean diseases. However the trouble ^ McClintock, J. A., Phytopath. 6 : 436-441, 1916. 264 Diseases of Truck Crops depends on weather conditions. It is most prevalent during periods of heavy night dews, or during pro- longed rains, and in hot muggy weather. Symptoms. Anthracnose is so characteristic, that it cannot be mistaken for any other disease, except perhaps the blight. In light attacks, the seeds are covered with sunken brown to black specks. These are especially evidenced on the black seeded varieties. In severe attacks, the seeds are covered with deep sunken black spots which are rifted in the center. On the leaves the disease attacks the veins, which become blackened and somewhat shrunken. Fre- quently it attacks the petioles, especially at the point of leaf attachment. In this case the foliage drops off, leaving the bare petioles or stems. Anthracnose on the leaves begins as small, circular, pin-point, dark red spots which enlarge, and later elongate into maroon colored pits, cracks, or cankers (fig. 47 e). On young seedlings the stem rots off a short distance above ground. The Organism. Spores are formed on the spots or cankers on all parts affected (fig. 47 f). These are imbedded in a gelatinous substance and can become loosened only by rain splashing or dew. It is at this stage that the disease becomes serious, since it is then spread about from plant to plant. When the spores are lodged on a new bean plant or on a new part of the same plant, infection takes place through the penetration of the germ tube of the germinated spores. It is estimated by Edgerton' that from one ' Edgerton, C. A., Louisiana Agr. Expt. Sta. Bui. 119 : 3-55, 1910. Family Leguminosae 265 half to^a million spores are formed on one infected pod alone. The period of incubation usually varies from four to six days. In culture media, the growth is at first white, but it soon becomes jet black in color. The mycelium of the fungus is hyaline, small at first, but later be- coming larger and darker. Control. Spraying has not given satisfactory results. The best control is to plant clean seed se- lected from clean pods. The latter before shelling may be dipped for ten minutes in a solution of one part of corrosive sublimate to a thousand of water. The treated pods are then dried in the sun, shelled, and the seed put away in dry mason jars until the following spring. Should weevils threaten these seeds, they may be fumigated with carbon bisulphide. By reserving a plot destined for bean seed, by care- fully destroying infected plants, and by selecting clean pods and seed, anthracnose and blight may be kept in check. Under no circumstances should an infected field be cultivated in damp weather, or when the dew is still on the plants. When this is done the spores of the fungus are scattered broadcast in the field. As for resistant varieties, there is very little to select from. However, Barrus^ found that the Wells red kidney bean is most resistant to anthracnose. It is therefore recommended for trial in localities where anthracnose prevails. In selecting for seed resistant varieties, these must of course be artificially inoculated ^ Barms, M. F., Phytopath. 5 : 303-311, 1915. 266 Diseases of Truck Crops with spores of the fungus. This will make sure that the parasite has been placed on the host. If there is any difference in resistance, it will be evidenced by the amount of infection developing on each variety tested. In this connection it should be remembered that there are numerous strains of C. Ihidemuthianum, some of which are very virulent while others are less so. In inoculating for resistant varieties, an attempt should be made to secure pure culture strains from various localities. Stem Anthracnose Caused by CoUetotrichum caulicolum H. and W. A serious stem rot attacks the Kentucky Wonder bean. The disease differs from anthracnose described above in that the former destroys the stems of the plant. Observations made by Heald and Wolf' show that the disease girdles the stem, and also causes deep fissured cankers on one side of it. The trouble has been found in only one locality in Texas, and it is doubtful if it is prevalent elsewhere. Little is known of the control of this disease. Angular Leaf Spot (fig. 47 g), see Cowpea, p. 271. Southern Blight, see Pepper, p. 305. Root Rot (fig. 49 a), see Rhizoctonia, p. 45. Texas Root, see Sweet Potato, p. 175. Root Knot, see Nematode, p. 49. • Heald, F. D., and Wolf, F. A., U. S. Dept. of Agr. Bur. PI. Ind. Bui. 226 : 35-36, 1912. Fig. 48. Diseases of Lima Bean. a. h. c. different stages of downy mildew on pods, d. tuft of conidiophores and conidia of Phythophthora phaseoli, e. same as d. but greatly enlarged, /. g. conidia germinating by means of a germ tube, h. i. j. k. germination of conidia by means of zoospores, /. germinating zoospores {d. to /. after Thaxter), m. n. fertilization of the oogonium by the antheridium, o. Phoma blight on foliage, p. Phoma blight on pods (o. and p. after Halsted), r. mature oospores of P. phaseoli {a. to c, m. n. and r. after Clinton). Family Leguminosse 267 DISEASES OF THE LIMA BEAN {Phaseolus lunatus var. macrocarpus) Lima beans, whether climbing or dwarf, are usually considered hardy. This is generally true under favorable weather conditions. But in hot moist weather, truckers may lose heavily from various diseases. Blight, see Bean, p. 260. Downy Mildew Caused by Phytophtora phaseoli Thax. Perhaps the greatest damage in wet seasons to lima bean culture of both the pole and the dwarf varieties is downy mildew. The damage from this disease equals that from the anthracnose on snap and other varieties of Phaseolus vulgaris. Symptoms. It is most conspicuous on the pods, where it forms a dense, dirty white mycelial growth (fig. 48 a-c). The trouble appears first on one side of the pod, and then works its way through to the other side. Infected pods wilt, shrink, and eventually dry up and die. In early cases of infection, the dis- eased area is separated from the healthy by a purplish border. Occasionally the blossoms are affected, in which case they wither and drop off. On the leaves the disease is manifested as irregular purplish dis- coloration, especially on the veins, but there seems to be no evidence of the fungus growth on it. 268 Diseases of Truck Crops The Organism. The mycelium is hyaline, non-sep- tate, and in other respects not different from other downy mildews. The conidiophores are long and little branched (fig. 48 d, e), the conidia are hyaline, elliptical to ovoid in shape, germinating by means of motile zoospores (fig. 48 f-1). The oospores or sexual resting spores are formed in the same way as in Pythium (fig. 48 m, n, r), see p. 43. Control. Downy mildew is carried over in the seed as dormant mycelium. Hence all shriveled seed should be discarded. In badly infected fields, crop rotation should be resorted to. The burning of trash and old bean plants is also advised. Finally three sprayings with 4-4-50 Bordeaux mixture during the growing season will keep the disease well in check. Rust, see Bean, p. 262. Powdery Mildew, see Bean, p. 262. Pod Blight Caused by Phoma suhcircinata E. and E. As the name indicates, the disease chiefly attacks . the pods. Blight is indicated on them by the appear- ance of large brown patches (fig. 48 o, p). The pycnidia of the fungus are arranged in concentric zones. In severe cases, the disease works from the pods to the seed, considerably reducing the yield. On the leaves the symptoms are the same as on the pods. Spraying with Bordeaux will control the trouble. ''%&>'' Fig. 49. Bean Diseases. a. Rhizoctonia root rot, b. root knot on lima beans. Family Leguminosas 269 Leaf Blotch Caused by Cercospora canescens E. and M/ This disease, so far as is known, is not generally distributed. It is found in certain trucking centers in Texas. On the leaves the spots are circular, but somewhat angular. The center of the spots is gray with a reddish brown border, the outside of which divides the diseased from the healthy tissue. The conidiophores are equally abundant on both surfaces, the spores are hyaline, straight or curved, slender and one to many septate. While no experiments have been made on the disease, spraying with Bordeaux is recommended. Leaf Spot Caused by Isariopsis griseola Sacc. The disease is confined to the foliage only. The spots produced are small and angular with no colored borders (fig. 47 h, i). On the under side of the leaf, the fungus forms a gray moldy growth on the spot, where large numbers of the spores are produced. The disease is not widely dis- tributed, and may be controlled by spraying with Bordeaux. Root Rot, see Rhizoctonia, p. 45. Texas Root Rot, see Sweet Potato, p. 175. Root Knot (fig. 49 b), see Nematode, p. 49. 270 Diseases of Truck Crops DISEASES OP THE COWPEA {Vigna sinensis) In the South, the cowpea is extensively grown as a truck crop. It is cultivated for its edible green pods, and dried peas, and often takes the place of the bean. Streak Caused by Bacillus lathyri Manns and Taub. Streak is a serious disease which until now has usually been mistaken for other troubles . The disease is the same as streak on the sweet pea and clovers. Symptoms. Like the bacteriosis of the bean, streak makes its appearance in a season of heavy dew. On the cowpea it usually appears just as the plant begins to bloom. It is manifested along the stems by light reddish brown to dark brown spots and streaks, the older of which are almost purple, having their origin usually near the ground. This indicates distribution by spattering rain and infection through the stomata or through insect injury. The disease becomes distributed quickly over the mature stems until the cambium and deeper tissues are destroyed in con- tinuous areas, and the plant dies prematurely. From the stem the disease spreads to the petioles, peduncles, and pods, the symptoms in these cases being similar to those on the stems. On the leaves, however, the disease appears as small circular spots, which grad- ually coalesce and eventually involve the entire leaf. When killed, the leaf presents a dark brownish ap- pearance. Family Leguminosae 271 The Organism. Bacillus lathy ri as worked out by- Manns, ' is rod-shaped, occurring singly, never found in chains, and seldom united by twos or fours, motile by means of flagella. It produces no spores, no capsules, no zooglea, liquefies gelatin completely in about three weeks, and produces no gas. Control. Rotation of crops is helpful; but since streak attacks numerous leguminous crops, such as bean and clovers, these should be excluded. Other methods of control are as yet unknown. Rust, see Bean, p. 262. Powdery Mildew, see Bean, p. 262. Angular Leaf Spot Caused by Cercospora crtienta Sacc; Cercospora dolichi E. and E. Angular leaf spot is a common disease on cowpeas. When it attacks the leaves, they are covered with angular ;rusty red spots, the leaves turn yellow and drop prematurely. On the stems the spots are ir- regular, elongated, dark colored, slightly sunken, and later forming cankers. The latter often crack and expose the stems to the attacks of various other parasitic and even saproph3rtic fungi. Under favor- able conditions of moisture, the spots on the leaves or stems are covered with a brownish downy growth made up of the conidiophores and conidia. No methods of control are known. ' Manns, T. F., Delaware Agr. Expt. Sta. Bui. io8 : 3-44, 1915. 2^2 Diseases of Truck Crops Wilt, Yellows Caused by Fusarium tracheiphila Ew. Sm. In the light sandy to loamy soils, wilt is the greatest drawback to pea culture. The disease is most pre- valent in the Southern States. Symptoms. It does not seem to attack young seedlings, but appears only when the plant is about six weeks old and upwards. In the field, scattered plants turn yellow and begin to drop their leaves, the stems become bare (fig. 50 a), and the plants finally die. On pulling out a diseased plant, the main root will apparently be sound, but the lateral rootlets will be dead, marking the seat of infection. A more definite symptom of wilt is a browning of the interior fibrovascular bundles of roots, stems, and petioles. This may be readily ascertained by splitting open lengthwise a root or stem of a sus- pected plant. The Organism. From unpublished work by the author, it is definitely proven that F. tracheiphila is distinct from Fusarium wilts of the cotton, okra, and watermelon. The Fusarium wilt of the cowpea is caused by F. tracheiphila, which produces only the conidial stage and has no relationship whatsoever with Necosmospora, or any other ascospore stage. The cowpea Fusarium may be found in fields which are also infected with okra Fusarium. In this case, the field is infected with two distinct organisms, thus making it sick to both cowpeas and okra. The cow- *** ^' i^K'"' « ik «f-^--^«. -■'A'f . 1--'' J ■1^ 'Vfr ^^-^ •-'ifl'- >.~^" ■•|»^."^"-*.>ai4^ Fig. 50. Diseases of the Cow Pea. a. Fusarium wilt, h. field of cow peas killed by Texas root rot, c. root knot, rf. row of iron cow pea resistant to Fusarium wilt in sick field where other varieties of peas have died (a. and d. after W. A. Orton). Family Leguminosae 273 pea Fusarium is parasitic only on the cowpea, and so far as is known does not attack any of the other cultivated legumes. Control. Diseased fields may be sown with beans or any other legume except cowpeas. Crops other than legumes may also be grown there. The develop- ment of resistant varieties is also a promising method of control. Orton^ has already developed the Iron cowpea (fig. 50 d), a variety which is resistant to wilt and partly also to Nematode. Root Rot, see Rhizoctonia, p. 45. Texas Root Rot (fig. 50 b), see Okra, p. 175. Root Knot (fig. 50 c), see Nematode, p. 49. DISEASES OF THE GARDEN PEA {Pisum sativum) Like the bean and cowpea, the garden pea is sub- ject to numerous diseases, some of which are of great economic importance. However many of these dis- eases may be controlled. Stem Blight Caused by Pseudomonas pisi Sack. Blight is a new disease recently found by Sackett^ in the pea fields of Colorado. So far as is known, the ' Orton, W. A., U. S. Dept. of Agr. Bur. PI. Ind. Bui. 17 : 9-36, 1902. ^ Sackett, W. G., Colorado Agr. Expt. Sta. Bui. 218 : 3-43, 1916. x8 274 Diseases of Truck Crops trouble does not seem to occur in the other States where peas are extensively grown. In Colorado, blight has suddenly made its appearance on a pea area of 500,000 acres, seriously threatening the pro- fitable growing of the crop. Symptoms. On the stems and leaves (fig. 51 b) the disease may be recognized by watery olive green to drab brown spots and by yellowish watery bruises on the leaflets and stipules. The roots seem to be free from the attacks of blight. Infection seems to start on the stem, near the ground level, and from there to work upwards. Lower leaves are usually the first to die. Occasionally the infected plants send out new shoots below the infected area. The new growth is sometimes unmolested but ordinarily it too becomes blighted. The Organism. Pseudomonas pisi is a short rod, rounded at both ends, and motile by means of polar flagella. It produces no spores, no cap- sules, and no zooglea and no involution forms. It produces no gas, and can stand drying of thirteen days. Control. Certain varieties seem to be more re- sistant than others. The development of resistant varieties is recommended. All trash and diseased materials should be destroyed by fire and not fed to animals. It is not known if spraying will control this disease. In badly affected fields, spraying with Bordeaux may be tried. Damping Off, see Pythium, p. 43. Rust, see Bean, p. 262. Fig. 51. Diseases of the Garden Pea and Bean. a. Thielavia root rot, to the right diseased plant with no root system, to the left healthy, b. stomatal leaf infection by Pseudomonas pisi, c. Sclerotinia liberliana rot on bean pods, d. endospore of Thielavia basicola, e. chlamydospores of T. basicola. Family Leguminosae 275 Thielavia Root Rot Caused by Thielavia basicola Zopf . Root rot is a common disease in fields devoted to peas for a period of years. The trouble on the garden and field pea is identical with that on the sweet pea. Symptoms. Plants severely infected with Thie- lavia have practically no root system, since this is destroyed by the fungus as rapidly as formed (fig. 51 a). All that is left of the root system is a charred blackened stub. The diseased host constantly at- tempts to produce new roots above the injured part but these in turn also become infected. Such plants linger for a long time, but fail to set pods which are of any value. The Organism. The mycelium of Thielavia basicola is hyaline, septate, and branched. The mycelium becomes somewhat grayish with age. Three kinds of spore forms are produced — endospores (fig. 51 d), chlamydospores (fig. 51 e), and ascospores. Endo- spores are so called because they are formed inside a special thread of the mycelium. This is the spore form that commonly occurs in pure cultures of arti- ficial media and on the host. The endospore case is formed on terminal branches with a somewhat swollen base and a long tapering cell. The endo- spores are formed in the apex of this terminal cell and are pushed out of the ruptured end by the growth of the unfragmented protoplasm of the base. They are hyaline, thin walled, and oblong to linear in shape. 2"^^ Diseases of Truck Crops The chlamydospores are thick walled, dark brown bodies borne on the same mycelium as the endospores. This type of spore is formed in great abundance on the host and particularly within the affected tissue. The ascospores are lenticular in shape and are borne in asci or sacs within black perithecia. This stage however has not been found on the pea or in pure cul- ture. Control. Thielavia hasicola is a soil-inhabiting fungus. With infected pea fields, soil sterilization is of course out of the question. The method of control suggested is crop rotation. Investigations by John- son^ have shown that the following vegetable crops are not subject to Thielavia root rot: potato, sweet corn, sweet potato, cabbage, onion, parsnip, carrot, beet, eggplant, and peppers. These crops may there- fore be safely used in a crop rotation, the system of which is best worked out by the trucker himself. Powdery Mildew, see Bean, p. 262. Pod Spot Cansedhy SphcErella pinodes (Berk. and Bl.) Niessl. Pod spot is a disease which is of even greater eco- nomic importance than Thielavia root rot. The disease does not confine itself to the pods alone, but also involves the leaves and stems. The trouble however is known by truckers as pod spot. ' Johnson, J., U. S. Dept. of Agr. Jour. Agr. Research, 7 : 261-300, 1916. Family Leguminosae 277 Symptoms. On the stem the trouble appears as numerous elongated lesions. These spread to such an extent as actually to girdle the affected stem. On the leaves are formed oval spots, grayish in the center, and limited by a dark band. The pods too become badly attacked and the symptoms there resemble those on the stems. The disease works its way from Ihe pods to the seed within. I'he Organism. The causative fungus has two spore stages. The pycnidia bear the hyaline, two celled spores and are formed within the dead tissue of the affected stems, leaves, or pods. The pycnidial stage is known as Ascochyta pisi Lib. The winter or ascospore stage has only recently been discovered by Stone, ^ who found it on pods and stems previously affected, and on culture media. The fungus may be carried from year to year as dormant mycelium within the seed, or in the ascospore stage. Control. Seed treatment will not be of any value since the fungus is hidden within the seed. No out- side treatment is capable of reaching the parasite within. Seed should be secured from localities known to be free from the disease. Rotation of crops • is also recommended. Giving the field a rest from peas or hairy vetch for at least three years is recommended. In badly affected local- ities, susceptible varieties, such as French June, Market Garden, American Wonder, should be dis- carded. The Alaska variety is claimed to be more resistant. ' Stone, R. E., Annales Mycol., lo : 564-592, 1912. 2/8 Diseases of Truck Crops Septoria Leaf Spot Caused by Septoria pisi Westd. The disease greatly resembles pod spot. But a microscopical examination of the fruit of the two will reveal the difference. Septoria leaf spot is of little economic importance. Root Rot, see Rhizoctonia, p. 45. Root Knot, see Nematode, p. 49. WEEDS Of the numerous legume weeds, few if any are troublesome in trucking. None are likely to be carriers of the diseases which attack beans and peas. CHAPTER XVIII FAMILY LILIACE-(E This family is an important one, since it furnishes such crops as asparagus, chive, garlic, leek, onion, and shallot. According to the Thirteenth Census of the United States, the total 1909 American area devoted to asparagus was estimated at 25,639 acres and the crop valued at $2,246,631. The States ranked according to largest area devoted to aspara- gus are as follows: California, New Jersey, Illinois, South Carolina, Pennsylvania, and New York. States with less than 1,000 acres are here omitted. The total area in the United States devoted to onions in 1909, including chive, garlic, leek, and shallot, of which there are no records, was estimated at 47,625 acres, and the total crop valued at $6,709,- 047. The States ranked according to acreage in onions were as follows: Ohio, New York, Texas, Cali- fornia, Illinois, Indiana, Louisiana, Massachusetts, Kentucky, New Jersey, Michigan, and Minnesota. States with less than one thousand acres are omitted. DISEASES OF THE ASPARAGUS {Asparagus officinalis) Asparagus may be considered a hardy host when grown under proper cultural and climatic conditions. 279 28o Diseases of Truck Crops Where this is not the case it soon becomes subject to a few, but serious, diseases. Leopard Spot Cause, Unknown. The disease, as the name indicates, consists of large irregular ashen colored spots, each surrounded by a dark border. No treatment which keeps the disease in check is known. Rust Caused by Puccinia asparagi D. C. Asparagus rust does not seem to be limited in its geographic distribution, as it has been found in all States where the crop is grown. It is especially se- rious in California, New Jersey, and all the other im- portant asparagus regions. Symptoms. Rust does not attack the asparagus tips which are cut for the market. It attacks the green tops which develop after cutting has ceased. Affected tops redden, and these when carefully ex- amined will reveal reddish rusty pimples or sori on the stems (fig. 52 a) and needles. In severe infection, the reddened tops become bright yellow, the needles fall off prematurely, exposing a bare dead stalk cov- ered with numerous rust sori. The symptom is generally found in September and the pimples are ^*^J^ .-^~^\ ' a ¥^^^^^iim^m Fig. 52. Asparagus Diseases. a. Asparagus rust on stems, showing sori with winter spores, 6. cluster cup stage of Puccinia asparagi. c. Uredo or summer spores of P. asparagi, d. Teleuto or winter spores of P. asparagi (6. to d. after R. E. Smith). Family Liliaceae 281 made up of the teleuto or winter spores of the fungus. In old asparagus fields, rust may appear early in the season. In this case instead of rusty brown sori there appear on the main stems and branches, but not on the needles, numerous bright cup-shaped bodies, containing the aecidial or spring spores. This form occurs about May but disappears in June or July. This stage is immediately followed by red pustules which contain the uredo or summer spores. Later in August and September, and as already stated the teleutospores appear. The latter help to carry the fungus over winter and unfavorable conditions. The effect of asparagus rust is an in- direct weakening of the crowns of the plant. Affected tips fail to store up the necessary starches and sugars for the underground crowns. The latter being un- der-fed become weak, soft, and subject to the attacks of various, soil-inhabiting parasites. TTie Organism. The life history of Puccinia as- paragi has been carefully worked out by Smith ^ and others. The mycelium of the fungus is long and narrow, extensively branched, deriving its food by means of suckers or haustoria which penetrate the cells of the host. The aicidiospores are formed in chains, coming up from the mass of mycelium at the base of the cup (fig. 52 b). The uredospores (fig. 52 c) are dark in color and are borne singly in the uredo pustules. Both the secidio- and uredospores are one celled, and both germinate by means of a germ tube which penetrates the host. The black rust or ' Smith, R, E., California Agr. Expt. Sta. Bui. 165 : 5-99, 1905. 282 Diseases of Truck Crops teleutospores (fig. 52 d) are two celled, thick walled, dark colored, and borne singly on long stalks. The teleutospores must first winter over before they can germinate. In germination each cell sends out a thick short germ tube which divides at the tip into four parts, each of which produces a side branch which bears secondary spores known as sporidia. The latter break away, and when falling on a fresh green asparagus top germinate by sending out a germ tube which penetrates the host. After proper incu- bation, the cluster cup stage appears, and the same life C3^cle is repeated over again. Control. Asparagus rust may be kept in check by taking advantage of certain cultural conditions. Rust is more abundant in seasons with insufficient rainfall or on lands which dry out rapidly, while soils which have an abundance of moisture harbor little or no rust. In moist soils, asparagus plants are more vigorous than those grown under dry conditions and vigorous plants are less subject to rust than weak ones. Irrigation, therefore, wherever possible will help to keep the rust in check. Rust infection can never take place unless there is plenty of dew to enable the spores of the fungus to germinate. In low lying places, dew formation is heavier and hangs on longer than in more elevated regions. As far as possible, asparagus should be grown on high, well exposed moist lands. In regions subject to rains and heavy dews, spraying is recommended. Sirrine^ has » Sirrine, F. A.. N. Y. (Geneva) Agr. Expt. Sta. Bui. l88 : 122- 166. 1900. Family Liliaceae 283 obtained good results by spraying with 5-5-40 Bor- deaux to which was added 2 gallons of a resin mixture (made up of 5 lbs. resin, i lb. potash, or lye, I pint fish oil, and 5 gals, water) to each 10 gallons of Bordeaux. Another good treatment is dusting the asparagus tops with flowers of sulphur. To be effective, this must be applied in the form of a fine smoke-like dust. If the tops are too dry they may be wetted with whale oil soap water, or the grower must wait for a heavy dew or rain. There are many ' ' dust sprayers" on the market, many of which have their good qualities. There are two main types of dust sprayers, the "seed sower" and the "fan blower." The former throws a tremendous dust cloud. The fan blower sends out small clouds and covers less area. The number of applications will depend on the amount of dew in the season. In general, three applications using one half a sack of flowers of sul- phur per acre during the season will suffice. The practice of applying ordinary salt (NaCl) to the soil will not injure the asparagus crop but it will fail to control rust. Resistant Varieties. It is a well-known fact that some varieties of asparagus are more resistant to rust than others. The Canovers Colossal which is the canning type is a variety which is badly subject to rust. The same is also true for the Columbian White and the Moore's Cross-Bred variety. On the other hand the Palmetto Type and the French or Argenteuil Barrs mammoth are fairly resistant. Natural Enemies. Puccinia asparagi, although 284 Diseases of Truck Crops itself a parasite, is in turn parasitized by three other fungi. 1. Darluca filum Cast. This fungus develops on the rust pustules, living directly on the mycelium and spores of its host. 2. Tuhercularia persicina Dilt. This fungus is not as common as the first one. 3. Cladosporium sp. This is a common fungus which is often abundantly found on rust pustules. All or any of these three natural enemies may be readily grown in pure culture and spread about broadcast wherever the rust is abundant and of economic importance. Damping Off, see Rhizoctonia, p. 45. DISEASES OF THE CHIVE {Allium schoenopo- rasum) Rust Caused by Puccinia porri (Sow.) Wint. This rust, though prevalent in Europe, has been reported but once in the United States by Clinton* as attacking also onions. It is characterized by a yel- lowing of the leaves which die prematurely. On care- fully examining the infected leaves we find the uredo pustules, which are minute, reddish, and covered with a reddish powder. The teleuto pustules are black and ' Clinton, G. P., Connecticut Agr, Expt. Sta. Rpts. 1909-1910 : 726. Fig. 53. Onion Diseases. a. Bacterial rot (after Stewart), b. Botrytis rot, c. healthy, d. Sclerotium rot, e. onion storage house, /. type r.f commercial storage houses, f;. interior of storage house, showing method of stacking crates (/. and g. after W. R. Beattie). Family Liliaceac 285 covered by the host epidermis. Chive rust is dis- tinct from the onion rust. DISEASES OF THE ONION (Allium cepa) The onion is commonly attacked by numerous dis- eases. Fortunately most of them may be controlled, by proper care, and timely preventive methods. Soft Rot Caused by Bacillus caratovorus Jones. The disease was first studied by Stewart, ' who how- ever did not determine the causative organism, but merely referred it to a species of Bacillus. The writer, however, was able to prove that soft rot of onions is caused by the same organism which causes a similar rot on carrots and other vegetables. The rot on the onion often starts at the neck of the bulb which is spoken of as " weak in the neck. ' ' Sound bulbs are hard at the neck, but when rot sets in, the outer layer remains sound while the interior tissue soft rots (fig. 53 a) . Sometimes a single scale is found rotted within the bulb, and the others apparently remain healthy. At other times a sound scale may be found between two rotted ones. Occasionally the rot is confined to the outer fleshy scale, in which case it is spoken of as "slippery onion. " In storage, ' Stewart, F, C, New York (Geneva) Agr. Expt. Sta. Bui, 164: 209-212, 1899. 286 Diseases of Truck Crops under proper conditions of ventilation and tempera- ture, the rot progresses very slowly. However, in poorly constructed houses the bulbs rot very fast and the disease then spreads by contact. Damping Off, see Pythium, p. 43. Blight, Downy Mildew Caused by Peronospora schleideni, Ung. Of all the onion diseases, blight (also known as downy mildew) is perhaps the most important from an economic standpoint. It may often wipe out from seventy per cent, of the stand to the entire crop. The disease usually accompanies muggy, damp, or rainy weather. Symptoms. The disease is best diagnosed early in the morning when the dew is still present on the foliage. Diseased parts have a peculiar violet tint. This is due to the downy cover of the fruit by the fungus. Soon the affected leaves lose their green color, becoming yellow in spots, and by the second or third day the}^ have all collapsed, and are entirely covered by the downy fruiting stalks of the causative fungus (fig. 54 a) . If the weather is unfavorable the disease will be seen to work in restricted spots in the field with the tops of the affected plants collapsed. However, after several days the diseased onions begin to recover by sending out new top growths. The previously diseased leaves now dry and break away. , n ^i;" Fig. 54. Onion Diseases. a. Downy mildew, b. mature conidiophore and conidia of Peronospora schleideni, c. fertilization of the female oogonium by the male antheridium, d. oospore (a. to d. after Wh^tzel), e. onion smut, /. spore ball of the smut fungus, g. spore germina- tion, formation of sporidia at x, h. Vermicularia anthracnose, i. section through acervulis of Vermicularia cirdnans. j. setae and spore formation in V . circinans {e. to g., i. and j. after Thaxter), k. pink root of onion, healthy and diseased bulbs, I. pink root of onion showing nipple formation, m. a formaldehyde drip attachment to a planet junior seed sower, n. a copper tank drip with flexible black tin tube and valve (m. and w. after Stone). Family Liliacese 287 The blight in this case does not entirely disappear. With the coming of wet muggy weather the epidemic may begin a new course. The seriousness of blight is usually overlooked by growers, because it usually works best when the onions have attained considerable bottoms. The latter are not disfigured or attacked in any way. But there is an indirect loss from the disease, because the food which is stored in the leaves is eventually des- tined for the bulbs. When the foliage is destroyed there is bound to be a reduction in yield of market- able onions. Tlte Organism. The conidiophores or fruiting stalks come out on the surface through the leaf stomata (fig. 54 a). The conidia are borne at the tip end of branches of the main fruiting stalk. They germinate by means of a germ tube. The oospores or sexual spores (fig. 54 c, d) are formed in the same way as in Pythium. The contents of the antheridium is emptied into the oogonium, and fertilization takes place. The oospore is thick walled, granular and oily within. The mycelium of the fungus is non-septate, hyaline, and derives its food by means of suckers or haustoria which it sends to the host cells. Control. Good results have been obtained by WhetzeP from spraying with Bordeaux. The form- ula recommended is 5-5-50. The number of appli- cations will vary with the climatic conditions and with the severity of the disease. It is doubtful if ' Whetzel, H. H., New York (Cornell) Agr. Expt. Sta. Bui. 218 : 139-161, 1904. 288 Diseases of Truck Crops one application will suffice; two to four applica- tions may sometimes be necessary, especially in low, wet, and poorly drained lands where the disease is severest. Smut Caused by Urocystis cepulce Frost. Next to blight, smut is the most important disease of the onion. The trouble is found wherever onions are grown, and it does not seem to be limited by climatic or soil conditions. Symptoms. Smut is at first characterized by dark spots on the seedling leaves (fig. 54 e). When held up to the light these spots are opaque. Later longi- tudinal cracks appear on one side of the spot, which widen, exposing within a fibrous mass covered with a black powder made up of the ripe spores of the fungus. Young infected seedlings usually die early. Those which survive later show smut pustules on the leaves and the outer scales of the bulbs. The disease may be carried from infected fields with the seed, with infected manure, and by man himself on infected soil particles adhering to his shoes or implements. The Organism. The spores of the fungus are able to retain their vitality for a long time, possibly twelve years. The spore ball (fig. 54 f) is made up of sterile cells and spores. The latter (fig. 54 g) germ- inate in the same way as spores of other smuts, see com smut, p. 252. Family Liliaceae 289 Control. A very effective treatment is to sow the seed in a seed bed and later transplant the sets. This method not only insures a crop free from smut, but the quality and the yield are benefited. An- other method which generally gives good results is to apply to the soil at sowing time from 500 to 700 gallons per acre of a solution made up of one pint of formaldehyde in thirty gallons of water. This is applied with a drip attachment of the seed drill. For this method to be effective the soil must be in good condition of tilth. Rust Caused by Puccinia allii D. C. Rust is a rare disease with onions in the United States, and very little is known about it. It is doubtful if it will ever cause damage serious enough to warrant treatment. Anthracnose Caused by Vermicularia circinans Berk. This disease seems to be confined to the bulbs only. It is characterized by black spots (fig. 54 h) which are made up of various rings one within the other. Each ring consists of minute black dots, which are the acervuli of the fungus and which pos- sess numerous black hairs or bristles (fig. 54 i, j). 19 290 Diseases of Truck Crops It causes the greatest damage under poor storage conditions. For methods of control, see p. 292. BoTRYTis Rot (fig. 52 b) is a storage trouble usually of little importance. Black Mold Caused by Macrosporium parasiticum Thuem. ; Macrosporium porri Ell. Black mold frequently follows injury from downy mildews or any other causes which weaken the plant. Spraying to control downy mildew will also prevent this disease. Bulb Rot Caused by Fusarium sp. This disease is usually a storage trouble; but the injury starts in the field and is favored by a wet sum- mer season. The rot is prevalent in Ohio and Con- necticut and possibly also elsewhere where onions are stored in bulk. It works inward, attacking the heart of the bulb so that the interior easily slips out. For methods of control, see p. 292. Sclerotitjm Rot or Black Neck Caused by Sderotium cepivorum Berk. Sclerotium rot is a serious storage trouble of white onions in Ohio. The disease seems to be favored by Family Liliaceas 291 improper storage conditions, and by early topping in the field where a green neck offers a favorable entrance of the rot. The latter is of a dry nature, and the affected bulbs become blackened and wrinkled at the neck (fig. 52 d). Selby' recommends treating the bulbs with formaldehyde gas as recom- mended for the white potato, p. 336. Pink Root Cause Unknown fungus.'^ Pink root is a serious disease which is threatening the onion industry in the Laredo districts of Texas. The disease apparently is not new, but it has not been investigated before. The work of the writer is as yet incomplete, hence no complete statement can be made at this time relative to the disease. The roots of affected sets first turn slightly yellow- ish, when they are known as "Yellow root, " and then pink. Affected roots dry up, and the bulbs con- stantly make an attempt to produce new rootlets, which even under favorable conditions become pink and die. At the end of the season and because of the attempt of the bulb to produce new roots, a nipple is usually formed at the bottom of the center plate of the bulb (fig. 54 1 and k). The disease is carried with the young sets from the seed beds to the field. It » Selby, A. D., Ohio Agr. Expt, Sta. Bui. 214 : 414, 1910. * Investigations by the author seem to show that pink root is caused by a pathogenic fungus. 292 Diseases of Truck Crops may also be introduced with infected soils clinging to the rootlets of the sets. Control. It is severest in fields where onions have been grown too long in the same field. Crop rotation will not control nor reduce the losses from pink root in the field. The use of new land, especially for the seed bed, is strongly urged. Pink root attacks the onion, chive, shallot, garlic, and leek. Onion Storage Since the greatest profits are derived when onions are sold at a time of greatest demand, it is necessary to store the crop. In the field, onions intended for winter storage should be allowed to ripen well. The degree of ripeness is indicated by a shriveling of the tops, and when the outer skin of the bulbs becomes dry before being pulled. The ripening process in the field may often be hastened by rolling a light roller on the tops to break them. After being pulled, the onions are allowed to lay in the rows for several days. They are occasionally stirred with wooden rakes to encourage an even drying of the bulbs. After the necks are clipped, the bulbs are put in crates and are either allowed to dry further in the field or they are carried to curing sheds where the crates remain for about two weeks until finally placed in storage. This method is preferred by most growers, as it is not desirable to expose the red and yellow varieties to the full sunlight in the field. The immature, Family Liliaceae 293 soft, or "thick necks" should be disposed of early, as they keep very poorly in storage. Good storage onions will rattle like wood blocks when poured out from the crate. After curing in the sheds, the bulbs are sorted over on the sorting racks where only the soundest are stored away. In some localities, onions are stored in pits. This may serve the purpose where only small quantities are grown. On a large scale storage plants (fig. 52 e-g) are in operation. Storage Conditions. The essentials necessary in storing onions are summarized by Beattie^ as follows: "Plenty of ventilation, storing in small quantities, a comparatively low temperature, dryness, and safety from actual freezing. " The construction of a storage house is not different from that of a sweet potato house, see p. 182. The house should be double walled throughout, with plenty of felt or paper lining. In this way a dead air space in all the walls will permit of more even indoor tempera- tures. Top ventilation is provided by means of roof ventilators. Bottom ventilation is secured by means of bottom windows or drain pipes built into the foundation at the surface of the ground. A false floor is also constructed inside, leaving an air space of about two to three inches from the main floor. The temperature of the storage house shotdd be as low as possible, but kept above the freezing point, i. e. above 32 to 36 degrees F. During severe cold ' Beattie, W. R., U. S. Dept. of Agr. Farm. Bui. 354 : 5-36, 1909, 294 Diseases of Truck Crops weather all openings should be closed. Occasionally heat may be necessary and this can be applied by stoves. Onions are often stored in bags or in slat bins holding lOO to 300 bushels each. However, neither bags nor bins are satisfactory. The best method is storing in crates. Of the Liliaceae weeds, the only one of importance is the wild garlic, Allium vineale. It, however, is not known to harbor any of the diseases which attack onions and its other closely related species. CHAPTER XIX FAMILY MALVACE^ This important family has but one plant which is of interest to the trucker, i. e. the okra. This crop is grown more in the Southern States. It is to be regretted that more of the people of the United States have not as yet learned its great food value. Accord- ing to the Thirteenth Census of the United States the area devoted to okra in 1909 was estimated at 347 acres and the value of the crops at $24,969. Of the few States which grow this crop may be mentioned Georgia, Texas, Louisiana, Florida, and North Carolina. DISEASES OF THE OKRA {Hibiscus esciilentus) Generally speaking, the okra may be considered a hardy plant. But it is subject to a few diseases which in severe cases may threaten the profitable raising of the crop. Leaf Spot Caused by Cercospora hibisci T. and Earle. The disease seems to be as yet restricted to Porto Rico. It is of no economic importance in the United 295 296 Diseases of Truck Crops States. According to Stevenson^ the trouble ap- pears as indefinite sooty patches (fig. 54 c) on the lower surface of the leaves. This saps the vitality of the foliage, causing it to turn yellow and to drop off prematurely. Great care should be exercised not to allow the above disease to gain a foothold in the United States. Wilt Caused by Fusarium malvacearum Taub.* Wilt is perhaps the main drawback to okra culture. The disease is found in light sandy soils, and some- times seems to work hand in hand with root knot. Symptoms. The disease does not seem to attack young seedlings. It is common on older plants, which however remain stunted as the disease works slowly. In severe attacks, however, the lower leaves wilt, droop, dry, and fall off. This is followed by a droop- ing, wilting, and falling off of the upper foliage, leav- ing thus a bare stalk, which eventually dries up. On pulling up a diseased plant, we find that the root system is apparently sound. But on splitting a diseased root and stem lengthwise the interior fibro- vascular bundles are found to be brown, indicating that the seat of the trouble is there localized. The Organism. Unpublished work by the author has definitely established that okra wilt is caused by ' Stevenson, J. A., Jour. Dept. Agr. of Porto Rico, i: 93-117, 1917. ' From unpublished work by the writer. W~^^9U^^ 'i. :i«d:a of buck-eye rot Phytophthora U-rns?r7s f TonidTa of /'. l,rre.uns, germmatmg by means of zoospores, g. zoospores.- h. matu;e oospores of P. lerreslrts. t. buck-eye rot {e. to i. after Sh«rbakoflF). m-iiure oospores "># Family Solanaceae 341 ammonium compounds. This is especially true on sandy loams. On the other hand, nitrate of soda or lime seems to check blossom end rot. Sunburn Tomato fruits are often burned while they are on the vines by strong sunlight beating on the exposed fruit. This results in a scalding of certain parts (fig. 67 e),loss of color, and a local drying which produces white spots with a dry peppery appearance. Such fruit is unfit for the market. Sunburn may also result from other and indirect causes. In dry sea- sons the tomato cannot supply the necessary supply of moisture to the foliage and fruit. As a result, they become weakened and contain numerous starved areas which dry up when exposed to strong sunlight. The same result may also be brought about by the in- direct action of the numerous leaf and root diseases. Control. In sections where sunburn is prevalent, it is advisable to plant tomato varieties with dense foliage. The plants should be put out as early as possible so that the vines may attain their maximum before hot weather sets in. The soil should be prop- erly fertilized, and sufficient humus incorporated to hold the moisture during periods of high temperatures. Irrigation should be practiced wherever possible. Mosaic Cause Unknown. A lengthy discussion on mosaic has already been given on p. 83. Mosaic on tomato is a common field 342 Diseases of Truck Crops trouble, conspicuous on stalks, fruit, and leaves. On the leaves it is manifested as a mottling of yellow areas on the tissue between the veins. The unequal growth of tissue causes the leaves to warp and grow unevenly. In severe cases the normal leaflets are replaced by a filform or fern -like structure (fig. 64 a), with a striking dissected form. The blossom of the diseased plant usually drops off, and the few setting fruits are small and deformed. Southern Wilt Caused by Pseudomonas solanacearum Ew. Sm. Southern wilt has a wide distribution. As its name indicates, it is generally found in the more southern States. It is generally severe in Texas, Alabama, Georgia, Mississippi, North and South Carolina, Florida, Maryland, Virginia, New York, and Connecticut. Symptoms. Infected plants usually wilt rapidly without losing their green color. In large leaves, the main axis is bent downward in a drooping way. With the young plants the stems and foliage also droop and shrivel. The vascular system of such plants is browned, indicating the presence of the causative organism within. In cutting across a freshly wilted stem, a dirty white to brownish white slime that is not sticky is seen to ooze out. In soft and rapidly growing plants, the whole pith is often converted into a watery slime. In tomato and egg- plants the disease seldom attacks the fruit but is Family Solanaceae 343 localized to the vegetative parts. With the Irish potato, the disease works underground where it also penetrates the tubers. These show a yellowing and blackening of the veins, finally giving way to a soft rot. On squeezing, a creamy exudate oozes out from the diseased veins. Southern wilt attacks not only the tomato, potato, and eggplant, but it also causes a serious disease on the tobacco, peanut, nasturtium, ragweed, im- patience, verbena, — plants which belong to families other than the Solanaceae. The Organism. Pseudomonas solanacearum is a medium-sized rod, with rounded ends and motile by means of polar flagella. Pseudo-zoogloeae are common in old cultures. No spores are formed; on agaragar, colonies are white, then dirty white, afterwards becoming brown with age. The or- ganism does not liquefy gelatin and produces no gas. Control. Crop rotation is the safest method of con- trol. All crops subject to wilt, such as potato and eggplant should be left out from the rotation system. Damping off, see Pythium, p. 43. Late Blight Caused by Phytophthora infestans (Mont.) De By. Late blight usually attacks the fall tomato crop. It is especially prevalent during rainy weather, where it may even be found in the seed bed. The trouble 344 Diseases of Truck Crops may be found wherever Irish potatoes are known to suffer from late blight, since the tomato and potato blight are caused by the same fungus. Symptoms. Affected plants appear as though killed by frost. The disease first shows itself as small blackened areas on the leaves (fig. 64 d), stems, and fruits. These rapidly increase in size and cause pre- mature death of the affected host. Fruits which may not show signs of disease will develop the trouble in transit if coming from infected fields. For a de- scription of the causative fungus, see late blight of potato, p. 322. Late blight of tomatoes may be con- trolled by spraying. The best results are obtained by using 5-5-50 Bordeaux. Spraying should begin with the rainy season. The ripe fruit should be cleaned by wiping off the Bordeaux stains with a dry cloth. Buckeye Rot Caused by Phytophthora terrestria Sherb. Buckeye rot is a disease which attacks the fruit. The trouble seems to be new and has been recently described by Sherbakoff.^ So far as is known the disease has appeared only in Florida. Symptoms. The disease, as the name indicates, appears as a pale to dark greenish-brown zonate spots on the fruit (fig. 64 i) . The rot is hard and somewhat dry when the fruit is green, but becomes softer as the • Sherbakoff, C. D., Phytopath. 7 : 1 19-129, 1917. Family Solanaceae 345 tomato ripens. It usually begins at a point where the fruit touches the ground, which is most commonly at the blossom end, and might be mistaken for blossom end rot were it not for the characteristic zonations. The Organisms. The mycelium is at first continu- ous, then septate. Conidia (fig. 64 e-g) germinate by means of swarm spores. Chlamydospores are com- mon, oospores (fig. 64 h) common on commeal agar. Besides tomato fruit, P. terrestria causes a foot rot of citrus trees and a stem rot of lupines. Control. Tomato plants, as far as possible, should be staked. By preventing the fruit from coming into direct contact with the soil, infection will be avoided. Fruit destined for distant markets should not be packed as soon as it is brought in from the field. If possible it should be kept a few days to allow for possible rot to develop so that the affected ones may be culled out and destroyed. Yeast Rot Caused by Nematospora lycopersici Sch. Yeast rot, as the name indicates, is induced by a parasitic yeast. This little known trouble has been investigated by Schneider. ^ Symptoms. The disease is indicated by a slightly depressed reddish-brown spot. The epidermal area of the affected spot becomes indurated and shriveled. ' Schneider, A., Phytopath. 6 : 395-399, 1916; and in Phytopath. 7 : 52-53. 1917. 34^ Diseases of Truck Crops The greatest amount of rotting occurs within the fruit. The Organism. The parasite is a typical yeast. It produces arthrospores of non-gametic origin, asci of gametic origin (fig. 65 a-c). The ascospores are formed in two groups of four each, slender, one- septate, and each containing a motionless fiagellum. Little is known about the control of this disease. Fruit Rot Caused by Phoma destructiva Plowr. Fruit rot is found in Cuba, Florida, South Carolina, Kansas, and New York. If not checked, it will no doubt spread rapidly and add to the burdens of losses from other troubles. Symptoms. On the fruit the disease is charac- terized by conspicuous dark spots (fig. 65 e) on the side and at the stem end of both green and mature fruit. On the surface of the largest spots numerous dark pycnidia may be seen. Besides attacking the fruit, the disease may also attack the foliage, causing dark spots which resemble those on the fruit (fig. 65 d). Affected leaves shrivel, droop, and sometimes drop off. The disease seems to be unable to attack potatoes or peppers. The Organism. The mycelium (fig. 65 h) forms a denvSe network of fungal threads within the host tissue. The pycnidia (fig. 65 g) are subglobose, car- bonaceous, smooth, slightly papillate, and with a dis- tinct central pore. The pycnidia are scattered and l^s.. ;■> :)< v\ ..-i J •;^'-^ it». ^Vif. Fig. 65. TOiMATO Diseases. of the PhomiFun^uTh ,^:^ y ^'^ ™* organism g. cross-section of a pvcnidium tne i-noma tungus, /;. mycelmm. t. pycnospores of same (d. to Z. after Ja^ieson). ^^.■*r*'>*lX Fig. 66. Tomato Diseases. a. Septoria leaf spot, b. section through a pycnidium of Seploria lycopersiii (after Levin), c. section through acervulus of Collelolrichum phoinnidfs (after Venus Pool), d. and e. Melanconium rot. /. section through an acervulus of the Melan- conium fungus (d. to/, after Tisdale). Family Solanaceae 347 possess a thin wall; the pycnospores (fig. 65 i) are hyalin and one-celled. Jamieson^ failed to find an ascus or winter stage. Should the disease become serious, spraying with Bordeaux is recommended. Leaf Spot Caused by Septoria lycopersici Speg. The disease is generally known as late blight, or blight, both of which names are misleading. Recent investigations by Levin ^ confirm the belief that leaf spot is widely distributed. It is found in Alabama, California, Connecticut, Delaware, Illinois, Louisiana, Massachusetts, Maryland, Michigan, Missouri, New Jersey, New York, North Carolina, Ohio, Penn- sylvania, Virginia, Tennessee, Texas, and Wisconsin . Symptoms. The first indications of the disease are minute water-soaked spots on the underside of the leaves. With time these increase in size and become circular in outline with a definite margin (fig. 66 a) . The spots become hard, dry, dark, and shrunken, and when numerous they coalesce into large blotches, in- volving the entire leaflets and leaves ; the latter soon droop, dry, and cling to the stalk, until broken off by the wind or by any other jar. Within the spots are formed minute black glistening pycnidia and the spores exude as yellowish mucilaginous drops. On the stems the spots are similar to those on the leaves, although they are not so clearly defined, nor ' Jamieson, C. O., U. S. Dept. Agr. Research, 4 : 1-20, 1915. ^ Levin, E., Michigan Agr. Expt. Sta. Tech. Bui. 25 : 7-51, 1916.. 348 Diseases of Truck Crops do they work in deep to form cankers. Spots may also occur on the calyx and on the fruit. The dis- ease, however, is usually a foliage trouble. Of the more resistant varieties maybe mentioned Mikado, King Humbert, Wonder of the Market, and Up to Date. Of the medium resistant varieties may be mentioned Alice Roosevelt, President Garfield, Pre- lude, Ponderosa, and Magnum Bonum. The Trophy and Ficarazzi are very susceptible varieties. The Organism. The mycelium of Septoria lyco- persici is hyalin, septate. The pycnidia are globose (fig. 66 b) ; the pycnospores are hyalin, needle-shaped, many-septate, and lose their vitality when exposed to ordinary room temperature for about four days. Control. The disease often starts on the seedlings in the seed bed. It is important therefore to start with a clean seed bed soil. Seedlings should be sprayed with 4-4-50 Bordeaux before being trans- planted. In the field the plant should not be worked in wet weather, or when covered with dew. Spraying with 4-4-50 Bordeaux is recommended, especially in wet weather. Since the causative fungus is carried over in pycnidia on dead leaves or stems, the burn- ing of all trash becomes necessary. Anthracnose Caused by Colletotrichum phomoides (Sacc.) Chester. Anthracnose is a disease to which ripe tomatoes are especially subject. The losses are often consid- erable both in the field and in transit. Family Solanaceae 349 Symptoms. The spots are at first small, but they soon enlarge. They are discolored, sunken, wrinkled, with distinct central zones, closely resembling the anthracnose of apple. In moist weather the spots become coated with a salmon-colored layer which consists of the spores of the fungus. The Organism. In structure C. phomoides is little different from other Colletotrichums. The setae of the fungus are very numerous, thus giving the acer- vuli a black appearance. The conidiophores are short, and the conidia, oblong, hyalin, and one-celled (fig. 66 c). Control. Anthracnose depends upon wet weather for its activity. Spraying with Bordeaux is recom- mended. Melanconium Rot Caused by Melanconium Tisdale Taub, Melanconium rot is a disease which attacks tomato fruit. Tisdale^ was the first to call attention to this trouble which he attributed to a species of Melan- conium. The writer has often had occasion to col- lect this disease on tomatoes in the Bryan (Texas) market. The origin of the fruits could not be exactly ascertained, but they were supposed to come from Florida, while others were home-grown. Infection experiments by the author affirm the parasitic nature of the organism, which is tempor- arily named Melanconium Tisdale Taubenhaus. ' Tisdale, W. H., Phytopath. 6 : 390-394, 1916. 350 Diseases of Truck Crops Symptoms. The disease is found both on partly green and on ripe fruit. The spots are brown to black, small, irregular, somewhat sunken, dry, and superficial, with the centers slightly raised (fig. 66 d-e). The Organism. The mycelium is white, much branched, and closely septate, the septation however being largely influenced by food supply. The co- nidiophores are straight, short, closely packed to- gether, arising from a basal pseudostroma (fig. 66 f) . The conidia are borne singly at the apex of each co- nidiophore. The conidia are Phoma-like, minute, cylindrical, slightly rounded at both ends, greenish white in color, and germinate by means of a single germ tube produced at either end. Control. Nothing seems to be known of the control of this trouble. Little is known of its distribution. But since it has been found in Wisconsin by Tisdale, and in Texas by the writer, it seems to be of wider distribution than is generally recognized. Possibly it is usually mistaken for other tomato troubles. Leaf Mold Caused by Cladosporium fulvum Cke. Leaf mold is a tomato trouble which is very troublesome under greenhouse conditions. In some of the Southern States, however, it is found on field tomatoes. The disease is favored by damp, muggy weather. Symptoms. The mold appears as rusty cinnamon, Fig. 67. Tomato Diseases. a. Cladosporium leaf mold, b. conidiophores of Cladosporium fulvum c conidla of ^■Jr'r"""' i*)/"'^ '■ ^^l" Southworth). d. two plants artific"ally^nfected with Sderotium Rolfsn, e. sunburn, /. Macrpsporium rot. "ueciea wun Family Solanaccae 35 1 irregular, feltlike spots on the underside of the leaf (fig. 67 a), the upper part of which turns brown, then black, and the affected foliage finally curls and dies. Control. Careful spraying with Bordeaux mixture will help to keep it in check. Black Rot Caused by Macrosporium solani E. and M. Black rot is a fruit trouble commonly found in dry weather and generally attacking ripe tomatoes. The spots are black, dry, slightly wrinkled, and ex- tending deep into the interior tissue (fig. 67 f). The mycelium of the fungus is at first hyalin to brown, then black. The conidiophores and conidia are dark, with three to six transverse and one to two longitudinal septa. Sleeping Sickness Caused by Fusarium lycopersici Sacc. Sleeping sickness is one of the most serious of tomato troubles. It is prevalent in New Jersey, Delaware, Maryland, Virginia, and in nearly every .Southern State. Symptoms. Infected plants become pale, the leaves wilt and droop and never recover (fig. 68). The droopiness of a diseased plant gives it a sleepy appearance, hence the name of the disease. On splitting open a diseased root or stem, the interior vascular bundles will be found to be brown. 352 Diseases of Truck Crops The Organism. F. lycopersici is a soil fungus which may be introduced with infected manure or seedlings. The fungus greatly resembles F. oxy- sporum. The conidia are hyalin to yellowish, fal- cate, acute. Control. Spraying will not control this malady since the parasite lives internally and cannot be reached by external applications. Long rotations in which the land is given a rest from tomatoes are recommended for at least ten years. The selection of resistant varieties may offer a means of conquering this trouble. Yellow Blight Caused by Fusarium orthoceras App. and Woll.; Fusarium oxysporum Schl. This disease is common on tomatoes in the Pacific Northwest. It has been investigated by Humphrey" and found by him to be caused by the two species of Fusaria above mentioned. Symptoms. It does not usually manifest itself until late, when the plants are blooming, or even when the fruits are partly formed. At first there is a slight twisting of the entire leaf, accompanied by a purpling of the veins. This is also followed by a rolling inward, and by drooping, but not wilting, of the leaflets and leaves. The foliage then take on glaucous greenish color, the fruit ripen prematurely, ^ Humphrey, H. B., Washington Agr. Expt. Sta. Bui. 115 : 1-22, 1914, .'4i,l Fig. 68. Sleeping Sickness of Tomato. Family Solanaccae 353 but the pulp lacks in flavor and taste. Affected plants cease growing, exhibit a thin, spindly growth, and cease producing. The disease is confined to the root system, which is slowly destroyed ; it becomes most virulent with the high temperatures. Both Fusarium orthoceras and F. oxysporum also induce a disease on the potato, see p. 327. Control. Both Fusaria produce an abundance of chlamydospores in the soil, thus making the eradica- tion of the disease very difficult. Long rotations seem to have no effect in controlling the trouble. Injuring the rootlets at transplanting seems to in- crease the amount of diseased plants. Definite methods of control are as yet lacking. Rhizoctonia Fruit Rot Caused by Corticiii/m vagum B. and C. var. solani Burt. This form of rot makes its appearance at the place where the fruit touches the ground. The diseased area becomes chocolate-colored, and the epidermis slightly wrinkled. The rot extends into the interior pulp turning it brown and dry. For further descrip- tion of the causative fungus, see p. 45. Southern Blight (fig. 67 d), see Pepper, p. 305. Root Knot, see Nematode, p. 49. 23 CHAPTER XXII FAMILY UMBELLIFERiE This family contains trucking crops which are of considerable economic importance. Of these may be mentioned the carrot, celery, parsley, and parsnip. According to the Thirteenth census of the United States, the area devoted to carrots in the United States in 1909 was 3764 acres, and the total crop was valued at $473,499, with New York leading in acreage. The area devoted to celery in 1909 was 15,863 acres, and the total crop estimated at $3,922,848. Of the leading celery States may be mentioned New York, California, Michigan, Ohio, Massachusetts, and Pennsylvania. The area in parsley in 1909 was 192 acres, and the crop estimated at $27, 181 . This crop is largely grown in Louisiana. The area in parsnip in 1909 was 722 acres, and the crop estimated at $102,- 674. Parsnip is grown mainly in New York, Massa- chusetts, Illinois, and Michigan. DISEASES OP THE CARROT {Daucus carota) Soft Rot, see Cabbage, p. 192. Root Rot, see Rhizoctonia, p. 45. 354 Family Umbelliferae 355 DISEASES OF THE CELERY {Apium graveolens) Soft Rot, see Cabbage, p. 192. Rust Caused by Puccinia hullata (Pers.) Schr. This rust resembles the rust of asparagus. The disease is unimportant, and is seldom met with in the United States. Leaf Spot Caused by Phyllosticta apii Hals. Leaf spot is a disease of minor importance. The trouble is characterized by dull brown patches on any part of the leaf. Spraying for late blight will also control leaf spot. Late Blight Caused by Septoria petroselini Desm. var. apii Br. and Cav. Late blight is perhaps one of the worst diseases of celefy. It may be found wherever celery is grown. In California, the greatest money losses to this crop are attributed to late blight. Symptoms. The disease first attacks the lower 356 Diseases of Truck Crops leaves of the stalk, producing irregular spots vv^ithout a definite boundary line. When the spots become numerous the foliage withers and dries up (fig. 69 a, b, c, d). The disease attacks the leaves as well as the stalks, rendering the affected plants useless so far as market is concerned. In storage, plants affected with late blight will keep very poorly or rot alto- gether. The Organism. The fungus mycelium is hyalin, septate. The pycnidia (fig. 69 e) are olivaceous, prominent, and abundant in the spots. The pycnidia are filifom, straight or curved, hyalin, and many septate. Control. According to Rogers,^ late bhght may be controlled by spraying with 5-6-50 Bordeaux. The first two applications should be given the seedlings in the seed bed. In the field the first spraying should be given about six weeks after trans- planting and continued once a month until the rainy season is over. With the advent of heavy rains, spraying should be done once every two weeks. Besides spraying, shading also seems to keep the diseavSe in check. In spraying celery great care should be exercised to use a sprayer which is operated by a pressure of not less than 1 50 pounds. Where this is overlooked, large drops of the Bordeaux mixture may be deposited on the leaves and stalks, which upon drying may deposit copper salt sufficient to harm the consumer. Sprayed celery should be carefully washed and dried before shipping. ' Rogers, S. S., California Agr. Expt, Stat, Bui. 208 : 83-115, 191 1. ^ IM di Fig. 69. Celery Diseases. a. Septoria leaf spot on leaf, 6. Septoria leaf spot on leaflet, c. Septoria lesions on ■jelery seed, d. Septoria spots showing pycnidial bodies, e. cross section showing pyncidium and pycnospores of Septoria pelroselini (a, c, and e after Coons and Levin). Fig. 70. Celery Diseases. a. Cercospora leaf spot, b. conidiophores and conidia of Cercospora apii (afterDuggar and Baily), c. Rhizoctonia root rot. Family Umbelliferae 357 Early Blight Caused by Cercospora apii Fr. Early blight is as common a disease as the late blight. In some seasons of heavy rains it is very destructive. It appears early and affected plants have little value for market purposes. Symptoms. The trouble first appears on the outer leaves as pale blotches visible on both sides of the affected parts. The spots are irregular, angular in outline, limited apparently by the leaf veins, with slightly raised borders (fig. 70 a-b) . The spots later turn brown to ashy white. Control. Early blight may be controlled by spray- ing with Bordeaux mixture as v/ith late blight. The Boston Market and Gold Heart should be avoided because of their susceptibility to the disease. The White Plume seems to be resistant. DISEASES OF PARSLEY {Carum petroseUnum) Drop, see Lettuce, p. 143. Late Blight, see Celery, p. 355. DISEASES OF THE PARSNIP {Pastinaca sativa) Early Blight, see Celery, p. 357. Root Rot (fig. 70 c), see Rhizoctonia, p. 45. Weeds Of the more important Umbelliferous weeds which truckers have to contend with may be mentioned 35^ Diseases of Truck Crops Wild Carrot {Daucus carsta) , wild parsnip (Pastinaca sativd), and poison hemlock {Cornium maculahim). All of these weeds should be eradicated by clean cul- ture. The first two especially help to carry the fungus of early blight, Cercospora apii. PART IV 359 CHAPTER XXIII METHODS OF CONTROL From the preceding chapters the trucker will be made well aware of the many crop diseases he has to deal with and of the numerous methods at hand to help him to control or keep in check most of the troubles. The methods of control may be classified as f ollov,''s : (i) Soil sterilization. This method has been dis- cussed under Chapter IV, page 53. (2) Seed treatment taken up in Chapter VII. (3) Spraying. (4) Crop rotation. (5) Development of resistant varieties. Spraying While the orchardist has learned the necessity of spraying, it is doubtful whether truckers have suf- ficiently realized its value. Spraying has two aims: to kill the insect and animal pests, and to con- trol fungous diseases. The substances which are used for the one purpose are without effect on the other. 361 362 Diseases of Truck Crops Insecticides All animal and insect pests are best controlled by the use of poisonous mixtures applied in the form of liquid sprays or of powders. Insecticides may be classified as internal or stomach poisons, and external or contact poisons. (a) Stomach Poisons. Paris green is one of the oldest of stomach poisons. When chemically pure, it is composed of copper oxide, acetic acid, and arseni- ous acid. It destroys cutworms, caterpillars, beetles, grubs, slugs, etc. It should be applied preferably as a liquid, using one pound of the poison and two pounds of lime to two hundred gallons of water. It tends to sink to the bottom of this mixture, unless constantly stirred while being applied. This chemi- cal is often adulterated with white arsenic, causing it to scorch the treated plants badly. Therefore for truck crops the use of arsenate of lead is to be preferred, since it is less liable to scorch the foliage, and it adheres better. Its chemical composition consists of acetate of lead and arsenate of soda. It is applied to the best advantage as a liquid, using about three pounds of powdered arsenate or five pounds of paste arsenate to one hundred gallons of water. Arsenite of zinc may also be used. It is a very finely divided fluffy white powder which distributes and adheres well to the foliage. It is intermediate between Paris green and lead arsenate in strength, and it costs less than either. Methods of Control 3^3 It is essential when arsenicals are used to see that they are correctly labeled, and kept under lock and key, as they are poisonous to man and animals. Hellebore or white hellebore is somewhat less dangerous than the arsenicals. However, it loses its insecticidal value by being exposed to the air. It is a specific against slugs. (b) Contact Poisons. All the tobacco or nicotine products sold principally as extracts or powders be- long to this class. A common brand much used is the preparation known as "Black leaf 40," diluted I part to 700 or 800 of water. An addition of ivory soap at the rate of two bars to each 100 gallons of the solution increases its effectiveness by making it spread out better. Aphine, sulpho tobacco, and a number of other products found on the market are usually valuable as contact poisons if properl}^ tested out and guaranteed by the deal- ers. Ordinary laundry soap, one pound to seven gallons of water, is very effective against all soft- bodied sucking insects. Fungicides These are poisons used to control fungous diseases. As previously stated, some parasitic fungi live on the surface of the leaves and stems and are therefore easily controlled. An example of this is the powdery mildew. Other fungi, and these are in the larger majority, are those which live parasitically within the tissue of the host, and therefore cannot be reached 364 Diseases of Truck Crops by any spray. Fungicides are helpful only in pre- venting entrance of the parasite in the host. They are as ineffective in controlling insect pests, as are insecticides in controlling fungous diseases. (a) Bordeaux Mixtures. This is the standard fungicide. The strength used for tender plants is three pounds of copper sulphate — also known as blue stone, — six pounds of lime, and fifty gallons of water. The easiest way to prepare it is to dissolve the blue stone thoroughly in twenty-five gallons of water. The best quality of unslaked lime should be used and slaked in a little hot water, care being taken, however, not to flood it while slaking, nor to let it become too dry. When the slaking is completed, enough water is added to make twenty-five gallons. The limewater and the blue stone solution are then mixed, pouring first one part of lime v/ater, then another part of the blue stone; the mixture is then strained and used at once. With crops with delicate foliage, such as watermelon, weak Bordeaux must be used to prevent burning of foliage (see page 243). For truck crops with less delicate foliage, the stand- ard Bordeaux mixture is 4-4-50 — that is, four pounds copper sulphate, four pounds unslaked lime, and fifty gallons of water. Stock Solutions. In spraying large areas, it is not always practical to weigh out and prepare the in- gredients at short notice. The trucker will therefore find it advantageous to prepare stock solutions so that large quantities of both dissolved copper sul- Methods of Control 365 phate and of lime may be ready for instant use. A stock solution of blue stone may be prepared as follows: Forty gallons of water are put into a fifty-gallon barrel; forty pounds of blue stone are placed in a basket and hung up so that the basket is half covered by the water in the barrel. As the blue stone is dissolved, each gallon of the water contains one pound of the chemical. In another barrel may be slaked forty pounds of fresh lime. Each gallon of that will contain one pound of lime. By keeping the slaked lime in the barrel covered with water and pre- venting it from evaporating, and also keeping the barrel with the blue stone solution covered to prevent evaporation, we shall have stock solutions ready for instant use. To make a 4-4-50 Bordeaux from stock solutions, for instance, it is necessary to take four gallons from the stock solution barrel with blue stone, and add this to twenty-one gallons of water. Four gallons are also taken from the stock solution barrel of slaked lime and added to twenty-one gal- lons of water. The two solutions of twenty-five gallons each are now added together, thus making a 4-4-50 Bordeaux. In this way it is easy to prepare an^?- fonnula from the stock solutions. To determine if the Bordeaux contains sufficient lime, the following test may be carried out. A few drops of potassium ferrocyanide are added to the Bordeaux mixture. If sufficient lime is present, no change will take place, but if the mixture is deficient in lime, a dark reddish brown color will appear where the drop strikes the liquid. This testing fluid is easily prepared by dis- 366 Diseases of Truck Crops solving one ounce of potassium ferrocyanide in about eight ounces of water. This chemical costs but a few- cents in any drug store and will last a long time if kept in a tightly sealed bottle. Points to be Remembered In preparing Bordeaux the following points should be kept in mind : (i) Copper sulphate solutions must be kept only in vessels of wood, fiber, brass, bronze, or copper. They must not be kept in iron or tin vessels, as they will corrode them. (2) It is necessary to use fresh stone lime, as air- slaked lime is useless. (3) Bordeaux mixture can be used only when freshl}^ mixed. If allowed to stand tvv^elve hours after making, it loses all fungicidal value. (4) Bordeaux mixture or lime should never be strained through burlap. The lint of the burlap is likely to work up into the nozzles and clog them. (5) Undiluted solutions of copper sulphate or lime should never be mixed together. (6) Bordeaux mixture should not be prepared with hot water. (b) Ammoniacal Copper Carbonate. The objection to the use of Bordeaux is that it stains the leaves and foliage. To avoid staining, colorless ammoniacal copper carbonate may take the place of Bordeaux. It is prepared as follows: Methods of Control 367 Copper carbonate 5 ounces Ammonia (26 Baume) 3 pints Water 50 gallons The best results are obtained when the copper car- bonate is first made into a paste with a little water. It is then dissolved by adding the ammonia, which is diluted with four quarts of water. If three pints of ammonia fail to dissolve all the copper carbonate, more may be used. Ammoniacal copper carbonate is only effective when used fresh. It loses its fungi- cidal value by standing, as the ammonia evaporates quickly. (c) Sulphur. Flowers of sulphur are often used to control powdery mildew or asparagus rust. It may be applied either by hand or with a duster. There are a number of other fungicides on the market which are not mentioned here. They should be thoroughly tested before they are used. Considerable discretion should be exercised before using a new fungicide which claims to be a "Cure all. " Combination Sprays In the foregoing chapters on diseases, it was seen that truck crops are subject to the attacks of more than one malady. Moreover, truck crops are also subject to the attacks of insect pests. It is therefore advisable to control both insect pests and fungous diseases at the same time. Spraying, if properly Tobacco Bordeaux extracts mixture yes yes yes yes yes no yes yes 368 Diseases of Truck Crops done, is effective in controlling or in keeping in check all the pests which attack truck crops. In combining a fungicide with an insecticide, v/e may accomplish two aims in one operation. The various spray mix- tures which may or may not be combined are in- dicated by Cooley and Swingle' as follows: Paris green Arsenate of lead Arsenite of zinc (ortho) Arsenite of lime Each of these preparations is mixed and applied just as if it were used alone. A combination of the am- moniacal copper carbonate with an arsenate would be unsafe, since the ammonia renders the arsenic more soluble, and hence may result in the burning of the foliage. However, it may be safely mixed with the tobacco products. Recent investigations by Professor Safro, Entomo- logist to the Kentucky Tobacco Products Co., indi- cate that ' ' Black leaf 40 " may be used in combination with such spray chemicals as lime-sulphur, arsenate of lead, arsenite of zinc, and iron sulphate, for con- trolling sucking and chewing insects and fungous dis- eases, the soap in this case being omitted. Professor Safro's work further claims that "Black leaf 40" may » Cooley, B. A , and Swingle, D. B., Montana Agr. Expt. Sta. Circ. 17: 119-151, 1912. Methods of Control 369 be safely combined with Bordeaux, and the desired results obtained. He writes as follows: "For pur- poses of spraying, add to every one hundred gallons of Bordeaux three fourths of a pint of ' Black leaf 40. ' As far as safety to the foliage is concerned, much greater strengths of nicotine may be added to the Bordeaux, but no additional effectiveness will be given to the mixture as an insecticide. Any nicotine solution which contains four hundredths of one per cent, nicotine will be effective in controlling plant lice, provided, however, the work is thoroughly done. " Proportions of Combined Sprays Bordeaux and Paris Green Paris Green ^ pound Bordeaux mixture 50 gallons Bordeaux and Ar senile of Soda Arsenite of Soda i quart Bordeaux mixture 50 gallons Bordeaux mixture must never be combined with kerosene emulsion, carbolic acid emulsion, and mis- cible oils. (d) Potassium Sulphide. Like sulphur this is a valuable fungicide for the control of the powdery mildew. The following strength is recommended: Potassium Sulphide 4 oz . Water 10 gallons 24 370 Diseases of Truck Crops Potassium sulphide is effective only if used imme- diately it is prepared. It loses its value by being exposed for any length of time. Stickers It is well known that with some plants, such as cabbage, spray mixtures cannot be made to stick. The use of a sticker added to the spray mixture will largely overcome this difficulty. A sticker may be prepared as follows: Resin 2 pounds Sal Soda (crystals). . . i pound Water i gallon The resin and the sal soda should be added to one gallon of water and boiled in an iron kettle for one and a half hours until clear. For plants which are hard to wet, such as cabbage, or onions, the amount of the sticker given above should be used for each fifty gallons of Bordeaux or ammoniacal copper car- bonate. For other plants, this amount is added to each one hundred gallons of the spray mixture. Principles Involved in Spraying It should be remembered that to destroy chewing insects, such as caterpillars, etc., the stomach poison must be evenly distributed all over the plant. This thorough spraying should be done as soon as the presence of the pest is suspected. Intelligent and observant growers will remember the time of ap- Methods of Control 371 pearance of the pest every year, although this date depends somewhat on the climate of each season. In destroying the green aphids, the contact poison should be distributed as evenly as possible on the insect itself. It is, therefore, best to spray for aphids when they are actually found working on the plants. To check chewing insects and fungous pests, however, the applications are made before the parasites appear. Before spraying it is necessary to have well in mind which organism is to be destroyed, and the proper ingredients to be used. To keep fungous pests in check it is necessary to have the plant covered with the fungicide all the time infection is feared or sus- pected. This spraying is preventive, protecting the plant from becoming infected. When the parasite has penetrated the host, spraying is of little value in saving the infected plant, although it will protect others which are as yet healthy. It is essential that the trucker be always ready to spray. Sometimes retardation for even a day may prevent the attain- ment of positive results. The timely destruction of one insect, or of one spore, means the destruction of countless generations of these pests. Thoroughness is as important in spraying as it is in everything else in life. Especially is this true for the control of fungous diseases. Spraying Machines Success in spraying often depends on the sprayer, and especially on the nozzle. In small scale garden- 372 Diseases of Truck Crops ing, an ordinary knapsack or barrel sprayer (fig. 71a) will answer the purpose. For trucking on large areas the use of power sprayers (fig. 71 b) becomes necessary. It is difficult to recommend the use of any one type when there are so many models on the market. After consulting various catalogues and examining types of spray machines at the county fairs and other exhibits, the grower will be in a posi- tion to determine the kind of apparatus best adapted for his conditions. A good power sprayer should be capable of maintaining a pressure of at least one hundred pounds while the nozzles are open. The sprayer should also have a convenient attachment for spraying four rows or more, and should also possess a device by which each row can be sprayed with either single or double nozzles. Moreover, all the working parts must be easily accessible, simple, and solidly built. Care of the Spraying Machine After each spraying the outfit should be emptied and carefully cleansed with water. Failure to do this will result in the corroding of the tank, rods, and nozzles. Crop Rotation Many of the soil diseases, such as root knot, Fusar- ium wilts, etc., may be economically controlled by crop rotation. If a certain disease gains a foothold in the soil, it is likely to become progressively serious, Fig. 71. Spray Machinery. a. A hand power pump, b. a power machine, rear view, showing arrangement for spraying three rows of cucumbers (after W. A. Orton). Methods of Control 373 as the particular crop which the disease attacks is grown for a number of years on the same field, the soil becoming thoroughly permeated by the mycelium and spores of the parasitic organism. If the infected land is planted with crops not subject to the disease, the parasitic organism will sooner or later die for want of a suitable host to live upon. For this reason crop rotation plays an important part in the control of numerous truck crops. To meet with success in rotation, the trucker must know what crops are subject to the disease to be controlled, so as to avoid them temporarily in the sick land. Weeds, too, are often subject to the same diseases as the cultivated crops. Crop rotation often fails if we overlook the importance of clean culture. Varieties Resistant to Disease It is a well-known fact that not all varieties of plants are alike subject to the same disease. In going over a diseased field, we find that while a large percentage of the plants may be dying, some few individuals will stand up and thrive in spite of the disease. If these individual plants are perpetuated in the same sick field, we may succeed in developing a strain or variety of plant which will produce one hundred per cent, healthy individuals in the same sick soil. On this principle are based the selection and development of resistant varieties. Much has al- ready been accomplished in this direction and still more is to be expected in the future. 374 Diseases of Truck Crops How to Develop a Resistant Variety This may be accomplished by selecting, from the sickest piece of land on which the crop is growing, the healthiest individuals, and taking the seed from them. The following year the selected seeds are again planted on the same infected land. The best in- dividual plants from this sowing are selected and their seeds saved. By continuing this method of selection for a number of years it may be possible to develop a strain which will yield one hundred per cent, of healthy plants in a sick soil. To maintain the purity of the selected strain as well as its resistance, it is necessary to reserve a plot of the sick soil, upon which the selected strain is grown for seed purposes. Care must be taken toward carrying any of the sick soil of this plot to other parts of the field. Drawbacks. With some crops and with certain diseases it seems hopeless to try to develop a resist- ant strain. If a variety is resistant to one disease it may be susceptible to several others, which are perhaps more serious. The resistance may often be local, in which case it becomes necessary to develop resistant types for each local condition. Resistant varieties often may not embody the requirements of the market. Nevertheless, the development of re- sistant strains should be tried wherever it gives any promise of success. CHAPTER XXIV CONTROL OF INSECT PESTS BY NATURAL FACTORS In this discussion we shall consider very briefly the natural factors which help in the control of parasitic insects. (a) Beneficial Predacious Insects. It is fortunate that nature always provides its own remedies. If insect pests were not kept in check by natural enemies the trucker who does not spray would be faced by tremendous odds in attempting to raise crops. The natural and beneficial enemies may be grouped, first, into parasites which develop within the body of the host, and second, predacious or those which feed externally. I. Of the first group may be mentioned a small wasp-like insect, Lysiphlebus testaceipes. This is no doubt an important parasite, which greatly helps to keep the green Aphis in check. Its life history was originally worked out by Webster, ^ and may be briefly summarized as follows : A mature female thrusts her ovipositor into the upper side of the Aphis and deposits a single egg ' U. S. Dept. of Agr. Bur. of Entomology Bui., no, 1912. 375 376 Diseases of Truck Crops within its body (fig. ^2 c-d) . The egg of Lysiphlebus hatches and soon begins to feed on the vital parts of the Aphis. The latter gradually ceases activity and finally dies and becomes mummified. When the larva of Lysiphlebus reaches maturity and pupates, it emerges through a circular lid cut on the back of the dead Aphis. Lysiphlebus is not active at tempera- tures below 56 degrees F. 2. Of the parasites which feed externally on Aphids may be mentioned the lady-bird beetle, of which there are several species. These actually de- vour great numbers of plant lice. Lady beetles need no description, as they are well known to all truckers. There are, of course, other important beneficial insects such as the Syrphid and the lace- winged flies. For a further description of these the reader should consult Webster's original publication already cited. (b) Beneficial Fungus Parasites. There are numer- ous species of fungi which from an economic consider- ation are very important. These live parasitically on numerous insect pests and undoubtedly greatly help in keeping them in check. Of these may be mentioned species of Empusa, and of Acrostalagmus, which live on Aphids or plant lice. Fungi which belong to species of Aschersonia are parasitic on the white fly. The fungus Botrytis rileyi is parasitic on numerous caterpillars. The fungus Cordyceps (fig. 72 a-b) contains some important species which are parasitic on the Harlequin bugs and other insect pests. The green muscardine fungus Metarrhizium Fig. 72. Parasitized Insects. Treatment of Fence Posts. a. Cabbage bug parasitized by Cordyceps nutans, b. cabbage bug parasitized by Cordyceps sobolifera (a. and b. after Lloyd), c. watermelon aphids parasitized by Lysiphlebus lestaceipes, showing circular holes on the backs of the aphids through which parasite emerged, d. a female of L. teslaceipes in the act of laying her eggs in the back of a green aphis (after Webster), e. Creosoted post after a period of service, I. a willow post treated 4 hours in hot creosote and 10 hours in cold; set June 13. 1005, examined November i, 1914, and showing practically no_ deterioration after 93-2 years' service. 2. A split soft maple post treated 4 hours in hot creosote and 10 hours in cold; set in lOOS and examined November 15, 1914. The post was set below the creosote line and some decay has entered beneath the creosote shell. 3. A 5-inch split Cottonwood post given a creosote bath treatment, set in 1905 and examined in 1914. The post shows practically no decomposition in either top or bottom. 4. An 8-inch ash post split in half, given butt creosote treatment of 6 hours in hot and 12 hours in cold, set 1905 and examined in November, 1914. The creosoted bottom is sound, penetration on the heart wood surface was less than in the sap wood. The heart wood portion of this post will undoubtedly give away first. The untreated top is in excellent condition. 5. A 4j4-inch untreated white cedar post after standing 93^2 years, /. A small treating tank in operation, {e. and /. after McDonald). Natural Factors Controlling Pests 377 anisoplicB is parasitic on numerous grubs and beetles. Most of these fungi, however, are onl}'' active during warm moist weather and cannot always be depended upon with certainty. CHAPTER XXV TREATMENT OF FENCE POSTS Whether trucking on a large or small scale, fence posts are always used to protect the crops from pas- turing animals or undesirable marauders. In buy- ing fence posts, the aim should be to secure those which naturally last longest. Posts of willow, Cottonwood, or soft maple will last far less than those of red cedar, osage orange, or the mulberry. Posts made largely of sapwood will rot much faster than those made of heartwood. All posts, before being used, should be rid of all their bark. The latter usually harbors insect and fungi which when active hasten destruction or decay. In order to preserve the life of fence posts longest, they should be treated with some good standard preservative. Creosote is the most important preservative for fence posts (fig. 72 e, I to 5). On a moderate scale, tanks (fig. 72 f) four feet high, three feet in diameter, and capable of holding thirty-five 4>2-inch posts should be used. The tank is raised about one foot above the ground to provide room for the fire box. The creo- sote is poured in the tank and the posts are allowed to remain in the hot preservative for a period of from two to six hours. The posts may then be allowed to •378 Treatment of Fence Posts 379 remain in the tank until the preservative cools off, or it is immediately transferred to another tank which contains cold creosote. This cooling off is necessary, as it causes a contraction of the remaining air and moisture in the wood structure. This causes addi- tional preservative to be drawn into the wood. Fence posts may be treated at any time of the year. The time of the year posts are cut affects only the seasoning, but not its durability. Posts cut in the winter are more difficult to peel. Contrary to general belief, winter cut posts contain more moisture and hence require longer seasoning. All posts to be treated must have all the bark removed. If the posts are cut in the spring, the peeling of the bark is very easy. Beveling the tops of treated posts is also recommended. This is especially necessary when the posts are treated at the butt end which is stuck in the ground. GLOSSARY A ACERVULI. Small groups of mycelial tufts upon which fungus spores are formed. ^ciDiosPORES. Spores of the rust family formed in an Eecidium. ^ciDiUM (secitmi). A cup-shaped body in which are formed the spring spores of certain rust fungi. AEROBE. Organism requiring air, more especially oxygen. AMMONiFiCATioN. The formation of ammonia at the expense of other forms of nitrogen compounds, by the action of microorganisms upon organic sub- stances, AMMONiFiERS. Microorganisms capable of transforming nitrogen compounds into ammonia. AMCEBOID. Like an amoeba, the creeping movement of which is made possible by appendage-like bodies. ANTHERIDIUM. The male sexual organ in fungi. APICAL. Terminal formation at the point of any struc- ture. ARTHROSPORES. Whole vegetative cells of either bac- teria or fungi, which by a thickening of their walls become resting spores. ASCOSPORES. Spores formed in an ascus. Ascus. A sac-like structure in which the winter spores of certain fungi are formed. 381 382 Glossary B BASIDIOSPORES. Spores formed on basidia. BASIDIUM. A straight stick like spore bearing fungal thread. CANKER. Definite dead area in the bark of stems or roots of plants. CAPITATE. Possessing a head. CARBONACEOUS. Dark to black colored. CHLAMYDOSPORES. Resting spores with very thick walls, formed within mycelial cells. CHLOROPHYLL. Green coloring matter in leaves of the higher plants. CHROMOGENic. Producing color. ciLL\TE. Fringed with hairs. COLUMELLA. Sterile axle of a pillar-like structure within a sporangium. CONIDIA. Spores formed asexually. CONIDIOPHORE. A spore-bearing fungal stalk. CONSTRICTED. Drawn together or contracted. CORTEX. Outer bark. CUTICLE. The outermost skin of plants. CYST. Sac or cavity. D DELIQUESCENT. Dissolving or melting. DIFFUSE. Loosely spread. DILATED. Enlarged. E ENDOSPORE. Spore formed within another cell. ENTOMOGENOUS. Living on insects. Glossary 383 ENZYME. An organic chemical product capable of bringing about chemical changes, but without itself undergoing any change, or entering into the final product. EXOSPORE. Outer covering of a spore. FALCATE. Sickle shaped. FLAGELLA. Whip-like appendage of protoplasm of bac- teria and swarm spores. FUNGUS. A plant of very low order. Its mycelium corre- sponds to roots and reproduces by means of spores. G GLAUcus. Sea green. GONIDIA. Algae-like cells. GUTTULATE. Drop-like. H HAUSTORIA. Special organs of a fungus used for attach- ment or for obtaining food. HOST. Any plant which nourishes a parasite. HYALINE. Translucent or colorless. HYPERTROPHiED. Part of diseased plant abnormally enlarged. HYPH^. Thread-like vegetative part of a fungus. INDURATED. Hardened. INFECT. To cause disease. INTERCELLULAR. Growing between the host cells. INTRACELLULAR. Growing inside the host cells. 384 Glossary LENTiCEL. A special loose corky structure in plants intended for the exchange of gases of the air and the interior of the plant. LESIONS. A definite diseased area. M MACROCONIDIA. Large conidia. MiCROCONiDiA. Very small conidia. MIDDLE LAMELLA. The Connecting or cementing mem- brane between any two cells of a plant. MYCELIUM. Vegetative threads or hyphse of a fungus. MYCOLOGY. The study of fungi. O OMNIVOROUS. Attacking a large variety of plants. OOGONIUM. Female sexual organ of fungi, containing one or more oospheres. OOSPHERE. Naked mass of protoplasm developing into oospores after fertilization. OOSPORE. Fertilized oosphere. PAPILLATE. Having wing-like structures. PARAPHYSES. Sterile filaments found in some fruiting forms of fungi. PARASITE. An organism living at the expense of another (the host). PATHOGENE. A disease-producing organism. PEDICILLATE. Bome on a stalk. Glossary 385 PERITHECIUM. A flask-shaped or globose sexual fruiting body containing asci. PERiTRiCHiATE. Flagella all over the surface. piONNOTES. An effuse conidial stage containing a maxi- mum of conidia and a minimum of aerial mycelium. PLASMODIUM. A mass of naked protoplasm with numer- ous nuclei and capable of amoeboid motion. POLAR FLAGELLA. Flagella borne at the polar ends of an organism. PROTOPLASM. The living substance of any plant cell. PSEUDOPiONNOTES. False pionnotes. PSEUDOSTROMA . False strom a . PUSTULE. A blister or pimple. PYCNIDIA. Sac-shaped fruiting bodies of a fungus in which the pycnospores or summer spores are formed. PYCNOSPORES. Summer spores of certain fungi which are formed in pycnidia. SCLEROTIA. Compact masses of mycelium in a dormant state. These help to carry the fungus over un- favorable weather conditions. SEPTUM. Any partition between two cells in the same fungus filament. SET/E. Bristle-shaped bodies. SOIL FLORA. Bacterial or fungus growth in a soil. SORUS. Heap of spores. SPORANGIOPHORE. Stalk-bearing sporangium. SPORANGiosPORES. Spores formed in a sporangium. SPORANGIUM. Free non-sexual bearing spore sac. SPORES. Seed of bacteria or fungi. STOMATA. Minute openings in the stems, leaves, or fruits of plants which serve as a medium of exchange of gases. 2$ 386 Glossary STROMA. A spore-bearing cushion composed of mycelium and sometimes of host tissue. SWARM SPORES. Spotes possessed with the power of motility. TELEUTOSPORES (teliosfores) . Resting or winter spores of certain rust fungi, U uredospores. Summer spores of certain rust fungi. V vesicular. Composed of vessels. VISCID. Sticky. zooGLE.^. Colony embedded in a gelatinous bed. zoosPORANGiA. Sporangia which produce zoospores. ZOOSPORE. A motile spore. INDEX Abbot, T. B., 30. Acid sick soils, 25 et seq. Acrostalagmus panax, 113. Actinomyces, 6. • chromogenus, 317. attacking beets, 120, attacking radish, 209. Alkali sick soils, 34 et seq. Allard, H. A., 84. Allium cepa, 285. schoenoporasum, 284. Alphano Humus Co., 20. Alternaria brassicce, 196. var. nigrescens, 2,23. panax, 1 14. Ammoniacal copper carbonate, 366. Ammonification, 14. Antheridium, 11. Aphis gossypii, 233. Apium graveolens, 355. Arthur, J. C, 117, 138. Artichoke, Globe, diseases of, 139 et seq. ■ Leaf spot, 139. Jerusalem, diseases of, 137 et seq. Downy mildew, 138. Leaf blotch, 138 et seq. Rust, 138. Ascochyta armorcbcicB, 205. hortorum, 302. pisi, 277. Asparagus (officinalis), 280. diseases, 279 et seq. Leopard spot, 280. Rust, 380. Asparagus, resistant to rust, 283. rust, natural enemies, 283. Atkinson, G., 43. Available nitrogen, elaboration of, 13. B Bacillus, 4. Bacillus carotovorus, 192. attacking onions, 285. — attacking salsify, 146. fluorescens liquefaciens, 14. putridus, 14. — — lathy ri, 261. on cowpea, 270. phytopthorus , 316. • mclonis, 221. mesenterictis vulgatus, 14,23. mycoides, 14, 23. pestijcr, 23. proteus vulgaris, 14. • ramosus, 23. subtilis, 23. tracheiphUlus, attaching cu- cumber, 229. Bacteria, distribution in soil, 6. forms, 4. influence of depth of cul- tivation, 8. number influenced by man- ure, 9. relationship to function of soil, 5. Bacterium teutlium, 118. Balm diseases, 256. Leaf spot, 256. Rust, 256. Barus, M. P., 265. Q^i 388 Index Bean diseases, 260 et seq. Anthracnose, 263. Blight, 260. Damping ofif, 261, Downy mildew, 261. Powdery mildew, 262. Rust, 262. Sclerotinia rot, 263. Stem anthracnose, 263. Streak, 261. Beattie, W. R., 293. Beet diseases, wj et seq. Crown gall, 118, 119. Damping off and root rot, 122, 123. Downy mildew, 123. Drop, 124. Leaf spot, 126, 127. Leaf spot and heart rot, 125, 126. Root knot, 129, 130. Root rot, 128. Root tumor, 121, 122. Scab, 120-121. Soft rot, 118. Tuberculosis, 120. Water core spots, 117. White rust, 123. Beneficial fungi, 376, Bessey, E. A., 51. Beta vulgaris, 117. "Black leaf 40," 368. Blinn, P. K., 224. Blossom drop, 82, 83. Bordeaux mixture, 364. Branch, G. V., 226. Brassica Japonica, 208. oleracea, 186. var. acephala, 207. var. botrytis, 202. rapa, 214. Bremia lactuccB, 141. Brown, N. A., 140. Cabbage diseases, 186 et seq. Black leg or foot rot, 195. Black mold, 196. Black rot, 190. Club root, 186. Damping off, 193. Downy mildew, 194. Drop, 194. Leaf spot, 196. Root knot, 199. Soft rot, 192. White rust, 193. Wilt or yellows, 197. storage decays, 199 et seq. Cantaloupe, 225. blight resistant, 225. care in shipping, 225 et seq. diseases, 219 ^^ seq. Anthracnose, 223. Bacterial wilt, 219. Cercospora leaf spot, 224. Cladosporium mold, 224. Downy mildew, 221. Leaf blight, 223. Mycosphaerella wilt, 222. Phyllosticta leaf spot, 224, Powdery mildew, 222. Root knot, 225. Soft rot, 221. Southern blight, 225. spraying, 232. Capnodium, 238. Carbon, transformation of, 13. Carrot diseases, 354. Root rot, 354. Soft rot, 354. Carum petroselinum, 357. Catnip diseases, 257. Leaf spot, 2^7. Stem rot, 257. Cauliflower diseases, 202 et seq. Bacterial leaf spot, 202. Ring spot, 204. Causes of diseases in crops, 71 et seq. Celery diseases, 355 et seq. Early blight, 357. Late blight, 355. Leaf spot, 355. Rust, 355. Soft rot, 355. Cercospora apii, 357, 358. armoracice, 207. canescens, 269. Index 389 Cercospora capsisi, 304. citrullina, 243. cruenta, 271. cucurbitcB, 224. dolichi, 271. hibisci, 295. Chive diseases, 284. Choanophora cucurbilarum, 235. Chrysophylyctis end obi oti cum, 319. Citron diseases, 234. Citrullus vulgaris, 234 et seq. Cladosporium julvum, 350. macrocarpum, 134. sp., 284. Clinton, G. P., 122, 124, 147, 215, 284, 323. Coccus, 4. Cochleaia armoracia, 204. Colletotrichum atramentariu :n, 325, 326 caulicolum, 266. Higginsianum, 214. nigrum, 303. phomoides, 348. Combination sprays, 367. Conidia, 12. Conn, J. H., 6. Contact poisons, 363. Convulvulus batatas, 151. Cooley, B. A., 368. Corticium vagum, 128. Cowpea diseases, 270 et seq. Angular leaf spot, 271. Powdery mildew, 271. Rust, 271. Streak, 270. Wilt or Yellows, 270. Crop rotation, 272. Cucumber diseases, 228 et seq. Angular leaf spot, 229. Anthracnose, 232. Bacterial wilt, 229. Damping off, 230. Downy mildew, 230. Mosaic, 228. Powdery mildew, 230. Root knot, 232. spraying, 232. Cucumis sativus, 228. Cucumis rmlo, 219. Cucurbita maxima, 234. moschata, 234. pepo, 234. Cutworms, 52. Cystopus canc?idM5, attacking rad- ish, 211. on horseradish, 205. ipomcBCB-pandurancE, 155. poriidacecB, 299. Cystospora batatas, 152. D Damping off, 42 et seq. Darlucafilum, 284. Daucus carota, 354. Denitrification, 24. Denitrified soils, 23. Diabrotica vittata, 220. Diaporthe battis, i^y, 159. Didlake, M., 20. Didymella catarice, 257. Diplodia herbarum, 258. — — herbicola, 257. tubericola, 16^. — — , attacking watermel- on, 239. Diseases of a mechanical nature, 72 et seq. — — of an unknown origin, 83 el seq. due to bacteria or fungi, 86 et seq. Dodder, 90, 91. Doryland Ch., 8. Drought injury, 78. Duggar, B. M., 12S, 298. Durst, C. E., 233. E Edgerton, C. A., 264. Edson, H. A., 209. Eggplant diseases, 300 et seq. Anthracnose, 302. Damping off, 301. Fruit rot, 301. Root knot, 303. Southern blight, 303. 390 Index Eggplant diseases — Continued Southern wilt, 301. Stem anthracnose, 303. Elliott, J. A., 154. Enlows, E. M., 229. Entyloma Ellisii, 133. Erysiphe cichoracearum, 232. galeopsidis, 258. polygoni, 216. , on bpan, 262. , on cantaloupe, 222. Family Agaricaces, 103 et seq. Araliaceas, 108 et seq. Chenopodiaccce, 1 16 el seq. Compositae, 137 et seq. Convolvulacese, 151 e< seq. Cruciferas, 185 et seq. Cucurbitacese, 21S et seq Graminese, 250 et seq. LabiatJE, 255. Liliacese, 279 et seq. Malvacese, 295 et seq. • Portulacaceas, 299. Solanaceas, 300 et seq. Umbelliferas, 254 et seq. Fence post treatment, 378. Fertility of soil, 16, 17 Fisher, O. S., 31. Fleet, W. v., 255. Formaldehyde, treatment of soil, 53, 54- Freiberg, G. W., 84. Frost injury, 74, 75. prediction, 76, 77. protection, 77, 78. Fuligo violacea, 152. Fungicides, 363. Fungi, structure and life history, 10. Fusariiim batatatis, 47, 157, 170. citrulli, 244. congliitinans, 197. cucurbita, 237. — — eumartii, 330. hyperoxysporum, 47 et seq. lycopersici, 351. niveum, 244. Fusarium orthoceras, 352. oxysporum, 327, 352. Poolensis, 244. radicicola, 329. trichothecioides, 330. ■ tuber ivorum, 331. G Garden pea, 275. diseases, 273 et seq. Pod spot, 276. Root knot, 278. Root rot, 278. Septoria leaf spot, 278. Stem blight, 273. Thielavia root rot, 275. Garman, H., 20. Gilbert, W. W., 74. Gilman, J. C., 198. Ginseng, no, 11 1, 113. — — diseases, 108 et seq. Acrostalagmus wilt, 113, 114 Alternaria blight, 1 14. Black rot, no, in. Bordeaux injury, 115. Damping off, 108. Downy mildew, 108, 109. Fiber rot, in, 112. Leaf anthracnose, 113. Papery leaf spot, 1 15. Root knot, 115. Stem anthracnose, 112. White rot, no. Gleosporium melongencE, 302. Glomerella piper ata, 303. Grossenbacher, J. G., 222. H Hail storm, 73, 74. Halstead, B. D., 125. Harding, H. A., 191. Harris, F. S., 35. Harter, L. L., 199, 301. Hawkins, 321. Headen, W. P., 16, 24. Heald, F. D., 139, 266. Healthy host and its require- ments, 63 et seq. Index 391 Healthy soil flora, nature and function, 12. Helianthus annuus, 148. tuberosus, 12,7. Heterodera radicicola, 48, 52, 332. attacking cabbage, 199- , . , attacking beets, 129. attacking lettuce, 146. attacking sweet pota- to, 176. Ileterosporium variabile, 134. Hibiscus esculentiis, 295. Hicks, G. A., 96. Higgins, B. B., 214. Hopkins, G. G., 31. Horehound diseases, 258. Leaf spot, 258. Powdery mildew, 258. Horseradish diseases, 204 et seq. Leaf spot, 207. Macrosporium black mold, 206. Root rot, 205. Shot hole, 206. White mold, 206. Humbert, J. G., 55. Humphrey, J. E., 232. Insecticides, 362. Iron, changes of, 15. Irrigation, methods of, 67 e( seq. Isariopsis griseola, 269. Istvanfli, G. De, 143. Jamieson, C. O., 331. Johnson, J., 57, 276. T., 320, 347. Jones, L. R., 74. K Kale diseases, 207, 208. Koch, Robert, 4. Lactuca saliva ^ 140. Lady beetles, 376. Leeuwenhoek, Anton van, 4. Lettuce diseases, 140 et seq. Bacterial blight, 140. Cercospora leaf spot, 145. Downy mildew, 141. Gray mold, 142. Leaf spot, 144. Lettuce drop, 143. Root knot, 146. Rosette, 146. Shot hole, 145. Levine, E., 347. Lightning injury, 74, 75. Lima bean diseases, 267 et seq. Blight, 267. Downy mildew, 267. Leaf blotch, 269. Leaf spot, 269. Pod blight, 268. Powdery mildew, 268, Root rot, 269. Rust, 268. Texas root rot, 269. Lutman, B. F., 318, Lycopersicum esculentum, 339. Lysiphlebus iesiaceipes, 375. M McClintock, J. A., 263. McCuUoch, L., 202. McKay, M. B., 127. Macrosporium herculeum, 206, 217. parasiticum, 290. porri, 290. solani, 325. sp., 304. Malnutrition, 80 et seq. Manns, T. F., 99, 195. Marrubium vulgare, 258. Marsonia perforans, 145. Meier, F. C., 239. Melanconium Tisdale, 349. Melhus, T. E., 212, 323. Meliotus alba, 20. 392 Index Meliotus denliculata, 20. lupulina, 20. Melissa officinalis, 256. Mentha virides, 258. Merrill, L. A., 65. Methods of control, 361. Mint diseases, 258. MonilochcBtes infuscans, 168. More, C. T., 226. Morse, W. J., 316. Mosaic, 83 et seg^. Muck or peat soils, 34 et seq. Mushroom diseases, 103 et seq. Bacterial spot, 103, 104. The Mycogone disease, 103 et seq. Mustard diseases, 208. Mycogone perniciosa, 104, 105. MycosphcBrella hrassicola, 204" citrulina, 22. N Nematospora lycopersici, 345. Nepeta cataria, 257. Niter-sick soils, 24. Nitrification, 14. Nitrobacter, 14. Nitrogen fixation from air, iS. — maintaining supply, 17. Nitrosococcus, 14. Nitrosomonas, 14. O O'Gara, P. J., 324. Okra diseases, 295 et seq. Leaf spot, 295. Root knot, 298. Root rot, 297. Texas root rot, 297. Wilt, 296. Olpidium brassicce, 193. Onion diseases, 285 et seq. Anthracnose, 289. Black mold, 290. Black neck, 290. Blight, 286. Bulb rot, 290. Damping off, 286. Downy mildew, 286. Pink root, 291. Rust, 289. Sclerotium rot or black neck, 290. Smut, 288. Soft rot, 285. storage, 292 et seq. Oogonia, 43. Oogonium, li, 43. Orton, W. A., 232, 273, 327. Ozonium omnivorium attacking okra, 297. attacking sweet pota- to, 175. Pammel, L. H., 46, 123. Parasitic fungi, 10. soil Fusaria, 46, 47. Parsley diseases, 357. Drop, 357. Late bhght, 357, Parsnip diseases, 357. Early blight, 357. Root rot, 357. Pastinaca saliva, 357. Penicillium expansum, 11. Pepper diseases, 303 et seq. Anthracnose, 303. Black anthracnose, 303. Fruit rot, 304. Leaf spot, 304. Southern blight, 305. Peppermint diseases, 258. Perithecium, 12. Peronospora effusa, 131, 132. parasitica attacking cab- bage, 194. schachtii, 123. schleidehi, 286. Pestalozziafunerea attacking gin- seng, 113. Phaseolus vulgaris, 260. Phoma betcB, 125. destructiva, 346. napobrassiccB, 215. olcracea, 195. solani, 324. Index 393 Phoma subcircinata, 268. Phomosis vexans, 301. Phosphates, changes of, 15. PhyUosticta apii, 355. batatas, 164. chenopodii, 133, 134. cucurbitacearum, 224. Physiological diseases, 80 el seq. Phythium de Baryanum, 42, 44, 193- attacking beet, 122. Phytophthora cactorum, 108. infestans, late blight of Irish potato, 322. late blight of tomato, 343- phaseoli, 267. terrestria, 344. Pisum sativum, 273. Plasmopora Halsledii, 138, 148. Plenodomus destruens, 159. Points to remember, 366. Pool Venus, 127. Poor seed, 92, 97. Potassium, changes of, 15. sulphide of, 369. Potato diseases, 306 et seq. Anthracnose, 324. Arsenical injury, 313. Black heart, 311. Black leg, 316. Black rot or jelly end rot, 329- Black wart, 319. Common scab, 317. Curly dwarf, 309. Early blight, 322. Fusarium wilt, 327. Hollow heart, 312. Internal brown spotting, 310. Late blight, 322. Leaf roll, 308. Melters or leak, 321. Mosaic, 312. Net necrosis, 311, Phoma rot, 324. Powdery dry rot, 330. Powdery scab, 314. Pox or pit, 313. Root knot, 332. Rosette, 331. Silver scurf, 326. Southern blight, 332. Southern wilt, 317. Spindling sprout, 310. Stem end rot, 329. Tip burn, 312. diseases, field control, 335, storage rots control, 333. Predacious insects, beneficial, 375- Pseudomonas beticola, 120. campestris, 190, 191, 205. attacking radish, 208. attacking turnip, 214. fluorescens, 103, 104. lachrytnans, 229. maculicola, 202, 203. pisi, 273. radicicola, iS et seq. solanacearum, attacking to- mato, 342. Stewarti, 251. tumefaciens, attacking beets, 118. viridilividum, 140. Pseudoperonospora cubensis, 230. Puccinia alii, 289. asparagi, 280. bullata, 355. helianthi, 149. attacking Jerusalem artichoke, 138. tragopogoni, 148. Purslane diseases, 299, Pycnidium, 12. R Radish diseases, 208 et seq. Black rot, 208. Club root, 208. Damping off, 209. Downy mildew, 211. Root knot, 214. Root rot, 214. Scab, 209. White rust, 211. Rainstorms, 73. 394 Index Ramularia armoracicE, 206. cynara, 138. Rand, F. V., 229. Rankin, W. H., no. Raphanus sativus, 208. Readhimer, J. E., 31. Reid, H. L., 134, 138. Resin, 370. Resistant varieties, 373. Rheosporangium aphaniderma- tum, 209. Rhizoctonia solani, 44. Rhizopus nigricans, 156, 158. attacking squash, 2,36. the cause of leak, 321. Roasting or pan firing, 56. Rogers, S, S., 356. Root knot, 48 et seq. Root rot, caused by Rhizoctonia solani, 45, 46. Rosenbaum, J., 109, no, 314. S Sackett, W. G., 24. Salsify diseases, 146 et seq. Rust, 148. Soft rot, 146. Southern blight, I48. White rust, 147. Sal 6oda, 370. Sanitary environment, 69, 70. Sarcina lutea, 14. Schneider, A., 345, Schrenk, H. von, 203. Sclerotinia libertiana, 45. attacking bean, 263. attacking beet, 124. attacking cabbage, 194. • attacking ginseng, 1 10. panacis, no. Sclerotium bataticola, 157, 173, 174. cepivorum, 290. Rolfsii, 44. ■ attacking cantaloupes, 225. 305. ■ attacking peppers, Sclerotium Rolfsii, attacking sweet potatoes, 174. attacking watermelon, 247. Seed, age of, 92. cultural conditions, 92, 93 . fertilizer effect, 95, 97. storage conditions, 94. testing, 95. treatment against insects, 97- treatment with formalde- hyde, 99. weight and color, 93, 94. Selby, A. D., 55, 291. Septoria bataticola, 165. consimilis, 144. lactuccB, 144. lycopersici, 347. melisss, 256. nepetcs, 257. pisi, 27S. Shamel, A. D., 54. Sherbakoff, C. D., 331, 344. Sick soil, treatment, 53. Sirrine, F. A., 282. Smith, E. F., 119, 190, 251. E. W., 230. R. E., 281. Smoke injury, 78 et seq. Soft rot, 236. Soil flora, action on mineral sub- stances, 14. Solonum tuberosum, 306. Spearmint diseases, 258. Spharella pinodes, 276. Sphceronema fimbriatum, 160, 173- Spinach diseases, 130 et seq. Anthracnose, 132. Black mold, 134. Downy mildew, 131, 132. Leaf spot, 134, 136. Malnutrition, 130, 131. Phyllostictaleaf blight, 133, 134- White smut, 133. Spinacia oleracea, 130. S pondylocladium atrovirens, 324, .-^26. Index 395 spraying, 361. machines, 370. principles involved, 370. Squash diseases, 234 et scq. Anthracnose, 237. Bacterial wilt, 234. Fruit rot, 235. Leaf spot, 237. Powdery mildew, 237. Root knot, 238. Root rot, 238. Soft rot, 236. Wilt or yellows, 237. Steaming sick soil, 54. Stevenson, J. A., 146. Stewart, F. C, 128, 285. F.G.,251. Stickers, 370. Stock solutions, 364. Stomach poisons, 362. Stone, G. E., 93. R. E., 277. Subirrigation, 67, 68. Sulphur, 367. Sunflower diseases, 148. Downy mildew, 148. Rust, 149. Surface or spray irrigation, 63, 69. Sweet potato diseases, 151 ct scq. Black rot, 160. Charcoal rot, 173. Cottony rot, 174. Dry rot, 159. Foot rot, 159. Java black rot, 165. Phyllosticta leaf blight, 164. Ring rot, 158. Root knot, 176. Septoria leaf spot, 165. Slime mold, 152. Soft rot, 156. Soil rot, 152. Soil stain or scurf, 16S. Texas root rot, 175. Trichoderma rot, 167. Vine wilt or yellows, 170. White rust, 155. methods of control, 176 et seq. Taubenhaus, J. J., 160 et scq. Temple, J. C, 9. Thick sowing, effect on damping off, 57- Thielavia hasicola attacking gar- den pea, 275. attacking ginseng, 1 1 1 . attacking horseradish, 205. Tinsley, J. D., 37. Tolaas, A. S., 103. Tomato diseases, 339 et seq. Anthracnose, 348. Blossom end rot, 340. Buckeye rot, 344. Damping off, 343. Fruit rot, 346. Hollow stem, 339. Late blight, 343. Leaf spot, 347. Melanconium rot, 349. Mosaic, 341. Rhizoctonia fruit rot, 353. Southern wilt, 342. Sunburn, 341. Yeast rot, 345. Yellow blight, 352. Tragopogon porrifoliiis, 146. Trichoderma koningi, 167. lignoriun, 167. Tubercularia persicina, 2S4. Turnip diseases, 214 et seq. Anthracnose, 214. Black rot, 214. Club root, 214. Macrosporium leaf spot, 217. Phoma rot, 215. Powdery mildew, 216. U Uredinales, 10. Urocystis cepulcB, 288. Uromyces appendiculatus, 262. Urophlyctis leproides , 121. 396 Index V Veihmeyer, P. J., 105. Vermicidaria circinans, 289. dematium, 112. Verticillium albo-atruni, 326. W Ward, M., 43. Water, need of plants, 64, 67. Watermelon diseases, 238 et seq. Anthracnose, 240. Bacterial wilt, 238. Blossom end rot, 247. Cercospora leaf spot, 243. Downy mildew, 238. Fruit rot, 247. Honey dew or sooty mold, 238. Malnutrition, 238. Mycosphcerella wilt, 239. Powdery mildew, 238. Root knot, 246. Stem end rot, 239. Vine wilt or yellows, 244. Whetzel, H. H., no, 287. White grubs, 52. Whitney, M., 64. Widtsoe, J, A., 65. Wind storms, 72, 73. Wire worms, 52. Wolf, F. A., 139, 235. Wollenweber, H. W., 331. Zea mays, 250. LIBRARY OF CONGRESS 002 81 5 860 9