THE UNIVERSITY OF ILLINOIS LIBRARY AGRICULTURAL LIBRARY UNIVERSITY OF ILLINOIS BULLETIN No. 223 CARNATION STEM ROT AND ITS CONTROL BY GEORGE L. PELTIER URBANA, ILLINOIS, SEPTEMBER, 1919 CONTENTS OF BULLETIN No. 223 Page INTRODUCTION 579 Stem Kot in Illinois , 579 Symptoms of the Disease 581 Carnation Branch "Rot 583 Infection 583 A STUDY OP THE CONDITIONS INFLUENCING THE GROWTH OF PARASITE AND HOST 584 The Fungus in Pure Culture 585 Persistence of the Fungus in Soils 586 Influence of Manures 586 Commercial Fertilizers 587 Acidity and Alkalinity of the Soil 588 Replanting 593 Temperature 593 Soil Moisture 595 ATTEMPTS TO CONTROL STEM EOT IN THE GREENHOUSE BY DISINFECTION AND STERILIZATION OF THE SOIL 599 Disinfection of the Soil -. 599 Steam Sterilization 602 CONCLUSIONS AND RECOMMENDATIONS . 606 BY GEORGE L. PELTIER, ASSOCIATE IN FLORICULTURAL PATHOLOGY 1 INTRODUCTION Carnation growing as a specialized industry in Illinois has assumed considerable proportions since its inception thirty years ago. It began in the vicinity of Chicago and the industry is still centered there. Other large establishments are scattered thruout the state, and no local florist is without a few benches of these plants. Accurate statistics are not available, tho it is a fair estimate to place the num- ber of carnation plants grown in Illinois for the trade in a single year at five million in the field and three million under glass. 2 Allow- ing three-fourths of a square foot for each plant, the total number of plants under glass would represent an area of about two million square feet, which is approximately one-fifth the total area of glass in Illinois. It is thus evident that several millions of dollars are invested in the carnation industry in Illinois. The carnation plant is attacked by a number of fungous diseases, several of which occasionally result in an appreciable loss to the grower. Perhaps the most serious of these is carnation stem rot. The following pages are devoted to a description of some experi- mental work undertaken by the author with the view of controlling this disease. A short discussion of the results, with recommenda- tions, is given at the end of the bulletin. STEM ROT IN ILLINOIS Carnation stem rot is caused by the attacks of a soil fungus, Rhizoctonia Solani Kiihn (Corticium vagum B. & C.). 3 The disease is widely scattered thruout the state, in fact, it is present to some extent in every greenhouse where carnations are grown. The controlling influences in the occurrence of stem rot ap- pear not to be due to unequal distribution of the fungus, but to be more closely related with climatic and edaphic conditions favorable to a Since September 1, 1916, Plant Pathologist, Ala. Agr. Exp. Sta., Auburn, Alabama. 2 Based upon replies to a questionnaire sent in 1915 to all Illinois growers having 5,000 square feet of glass or more. 8 A complete description of the general characters of this fungus, together with a historical account, its distribution, hosts, etc., will be found in Bulletin 189 of this station. 579 580 BULLETIN No. 223 [September, the spread and development of the fungus, together with the condition of the plant. The losses from carnation stem rot are not often very great. However, under conditions favorable to the rapid development and spread of the fungus, it becomes a destructive parasite. Under such conditions, many cuttings may be destroyed in a short time and many plants also lost, both in the field and later in the benches. In isolated cases the loss may be as high as 50 percent of the cut- tings. The percentage of loss may be equally high in the field and in benches. The average loss from season to season of course is much lower. From replies to questionnaires sent out by the writer to carnation growers in the state, it was learned that the percent- age of loss varies from .1 percent to 20 percent, with an average of 2.2 percent in the greenhouse and 3.25 percent in the field. In two of the experimental houses at the Illinois Experiment Station the loss averaged nearly 2 percent a year for a period of five years (see Table 1). TABLE 1. Loss FROM CARNATION STEM ROT IN THE EXPERIMENTAL HOUSES NOS. 1 AND 2, FOR A PERIOD OF FlVE YEARS Season Date of planting No. of plants Total loss Percentage loss 1909-10 Sept. 9-13 3200 33 1.03 1910-11 Sept. 9-12 3200 27 .84 1911-12 Aug. 8-10 3200 49 1.53 1912-13 Aug. 7-8 3200 99 3.09 1913-14 Aug. 12-14 3200 86 2.70 Practically all the soil used by the grower is inhabited to some extent by this fungus. The fungus is, in all probability, endemic, that is, it has not been introduced into the state with carnation plants but existed in the soils of Illinois before carnations were grown. This statement is supported by the fact that diseases due to the fungus are prevalent thruout the United States on many plants, and the fungus itself is found in many foreign countries. The fungus may live purely as a saprophyte in the soil, getting its nourishment from dead organic materials, or it may be parasitic, that is, living on and getting its sustenance from growing plants. In a previous publication 1 the writer has shown that the fungus may attack a large group of plants, including vegetable and field crops, herbaceous plants, and weeds, besides many plants grown under glass. The wide distribution, the many hosts, and the repeated reports of the destructiveness of the stem-rot organism prove very conclu- sively that it persists indefinitely under diverse conditions in arable J Loc. cit. 1919] . CARNATION STEM EOT AND ITS CONTROL 581 soils. However, it is only when conditions are favorable for its development that it becomes an active parasite. Owing to this fact, it is not .as serious as some of the Fusarium wilts, which once intro- duced into a locality, increase in severity each season until the growing of the crops attacked by them must be abandoned. SYMPTOMS OF THE DISEASE Stem rot may attack seedlings, cuttings, or mature plants. In ail cases the symptoms are more or less alike. When seedlings become affected (a condition commonly known as "damping-off "), lesions ap- pearing as small brown spots are seen on the stem at the surface of the soil. The lesions increase in size, eventually almost girdling the stem and causing the collapse of the seedling. In severe cases the prostrate seedlings may later appear overgrown with a mat of brown strands made up of the mycelium of the fungus. Cuttings are attacked several days after they have been placed in the sand. As in the case of seedlings, the cutting is attacked on the stem just above, or frequently just below, the surface of the sand. The leaves wilt, the cutting falls over, and a soft, wet, progressive rot may develop at the callus and extend to the surface of the sand, or lesions of various sizes may be formed at any point. Stem rot occurs to some extent on the young plants in pots. The source of this infection is either in the use of diseased cuttings or of contaminated pots. On pulling up these plants it is found that stem rot usually starts from a small lesion which increases in size until the stem is girdled. The symptoms shown by a mature plant attacked by the disease are very characteristic (Fig. 1). The fungus enters the stem at a point just below the surface of the soil. The foliage becomes pale, gradually losing the green color. In a few days or a longer period, depending upon the condition of the weather, this is accompanied by wilting. An examination of the stem at the surface of the soil reveals at this time a slimy, wet condition under the bark, which gives this rot its characteristic name. A slight twist is sufficient to slough off the bark and expose the harder tissues underneath. A plant at this stage may as well be pulled and removed, for it has been in- jured beyond recovery. The fungus evidently enters the plant thru the cracks in the corky layer of the bark at a point near the surface of the soil. After passing thru the bark it attacks the growing layer of cells, the cam- bium. From this tissue the mycelium passes into the woody tissues and can be found even in the pith. It is at this time that wilting becomes evident. During later stages, sclerotia, which are small com- pact masses of mycelium, are formed on the center portions of the stem and these become quite evident to the unaided eye. 582 BULLETIN No. 223 [September, FIG. 1. CARNATION PLANT SHOWING THE CHARACTERISTIC SYMPTOMS OF STEM EOT 1919] CARNATION STEM EOT AND ITS CONTROL 583 CARNATION BRANCH ROT There is but one carnation disease which may be mistaken for stem rot. To this disease the writer several years ago applied the .term "branch rot". Before that time the two diseases were com- monly known as wet stem rot and dry stem rot. In order to avoid confusion of these two terms, the term stem rot was adopted for the disease caused by Rhizoctonia and the name branch rot adopted to replace the term dry stem rot. Branch rot is caused by the fungus Fusarium. This disease affects the host plant much more slowly than does stem rot. There is no noticeably rapid wilting of the foliage of the entire plant. Infection does not, as a rule, take place at or near the surface of the soil but may take place at any point where the tissues have been broken. Branch rot is essentially a wound disease. Wherever a branch or leaf has been broken or removed, the disease may gain entrance. In- fected parts turn yellow, wilt, and become dry. A single branch may thus be affected, while the rest of the plant appears healthy and normal. There is no soft and slimy area on the stem, as is found in stem rot, but instead the stem remains dry and tough. Occasionally both diseases occur on one and the same plant. In the cutting bench the two diseases are not so easily distin- guished. However, careful observations will show that in the case of branch rot the foliage is most often affected and very little rotting is evident at or below the surface of the soil. In the case of stem rot, on the other hand, the disease is noticeable on parts of the plant at or below the surface of the soil. INFECTION Mature Plants. As said above, stem rot attacks seedlings, cuttings, and mature plants. Mature plants may become infected either in the field or in the greenhouse. From observations in the carnation field during four summers it has been found that, altho always present in the soil, the fungus attacks plants only under certain conditions. One of these conditions is the presence of wounds. Many counts in the field have brought to light the fact that plants with a single central stem, breaking one to two inches above the soil, are less frequently infected than are plants forking just at or slightly below the soil surface. The branches of the latter are easily broken during cultivation and many infections have been traced to such wounds. Stem rot is more prevalent during a hot, sultry, wet season. Such a season produces large, bushy plants, with much soft growth. It is very probable that infection takes place more readily under such conditions. 584 BULLETIN No. 223 [September, Perhaps the most critical period of the mature plant is at the time when it is transferred from the field to the house. The growth of the plant at this time is more or less checked, and unless the weather is cool the temperatures of the house may be unfavorably high. It is at this time, or shortly after, that large losses due to Rhizoctonia" occur. Losses at this time are unquestionably due to changed condi- tions, more or less abnormal until the plant has again become estab- lished, and to unavoidable injuries to the plant, such as breaking of branches, etc., during the process of transplanting. Cuttings. Cuttings in the sand succumb very rapidly to attacks of Rhizoctonia. The fungus may be introduced into the cutting bench by means of cuttings taken from plants already infected. Cuttings taken from the lower portions of the stock plant are most likely to harbor the fungus, especially when the leaves have been in contact with soil. Unclean sand also may be the means of infection. The source of sand used in the cutting bench is of much importance. Sand used previously for cuttings, unless disinfected, may harbor the fungus, which, when conditions are favorable, may become active and attack many cuttings. After the rooted cuttings have been transferred to pots, losses are not frequent. Individual plants may be destroyed by the disease, but such infection cannot be carried readily to adjacent plants. If the rooted cuttings are transplanted into flats, the losses frequently are more extensive, for a single infection may readily be carried to a number of plants. A STUDY OF THE CONDITIONS INFLUENCING THE GROWTH OF PARASITE AND HOST In attempting to combat a fungous disease, such as stem rot of carnations, two possible courses are open; either the fungus must be eradicated from the soil or, if that is not possible, some method must be found to reduce its destructiveness to a minimum. Attempt- ing the latter, two more or less clearly defined methods of procedure are possible; either the fungus must be placed in an environment which, being unfavorable, will greatly reduce its virulence but at the same time approximate rather closely the optimum conditions for the carnation plant, or carnation plants must be developed which are to a high degree immune from the attacks of the fungus. A series of experiments was undertaken by the author with the view of ascertaining some of the conditions which influence the growth of the fungus ; also the effect of these on its parasitism. Sim- ilar studies were made of possible methods of eradicating the fungus from soil in greenhouses. 1919] CARNATION STEM EOT AND ITS CONTROL 585 THE FUNGUS IN PURE CULTURE Temperature. In pure culture in the laboratory it was found that the fungus grows slowly at relatively low temperatures. At higher temperatures growth is more rapid, the most rapid growth taking place at approximately 86 degrees Fahrenheit. Moisture. It was found also that the fungus responds in a simi- lar way to moisture conditions. In relatively dry sand it makes good subsurface, growth. In wet sand growth is on the surface of the sand. This is probably correlated with aeration, especially with the supply of oxygen. Practically all injury caused by Rhi- zoctonia occurs at or near the surface of the soil and rarely below three or four inches, except perhaps in seed beds in which sand is used. This fact has already been discussed in detail in Bulletin 189, already referred to. The stem-rot organism is very resistant to unfavorable external conditions, such as low temperature and drying. An experiment was carried out by placing a set of flasks partially filled with sand which was inoculated with the fungus, in the open field. Another set of flasks containing some of the inoculated sand was placed in the green- house, while a third was kept in the laboratory. At different times during the winter months the flasks were weighed to determine the loss in water content. Cultures of the fungus also were made at the same time to determine whether it was still living. During the interim a minimum temperature of 12 degrees Fahrenheit below zero had been registered, and several flasks in the open field had been broken by the frost. In all cases the flasks had lost from 25 to 50 percent of their original weight. However, in every case the fungus survived and was able to make normal growth when trans- ferred to more favorable conditions. Cultures were made from flasks kept in the laboratory for two years and two months after they had been placed there, and the fungus was still alive. The sand at this time was dry and hard. Thus, low temperatures and drying appear to have little or no effect on the vitality of the fungus. Acidity and Alkalinity. As a number of writers have recom- mended the use of lime for the control of stem rot, the effects of acidity and alkalinity on the growth of Rhizoctonia in pure culture were tested out in the laboratory. String-bean agar was made acid and alkaline to various degrees, inoculated, and measurements of the growth of the mycelium taken from day to day. The results showed that Rhizoctonia can grow on medium which, is, within reasonable limits, either acid or alkaline in reaction. 586 BULLETIN No. 223 [September, PERSISTENCE OF THE FUNGUS IN SOILS Fortunately most growers renew the soil in the benches each sea- son. However, as some growers use the same soil, during a second season, a knowledge of whether the stem-rot fungus will persist in the soil in the bench from one year to the next is of importance. A five-foot section (No. 113) in the greenhouse was filled with soil taken from a bench in which carnations had been grown the previous season. The bench was planted to twenty Beacon carnation plants. A similar section (No. 112) was filled with fresh soil taken from a field that had been in sod for a number of years. This section was also planted to twenty Beacon plants. The two sections received similar treatment in the application of fertilizers and the cultural methods were uniform. During the entire growing season one plant died of stem rot in the section containing fresh soil (No. 112). Eight plants were lost in the section in which old soil was used (No. 113). The results are tabulated in Table 2. TABLE 2. EFFECT OF PLANTING CARNATIONS IN OLD INFECTED SOIL USED THE PREVIOUS SEASON: 1912-13 Sec- tion Treatment Number of diseased plants Number of healthy plants Percentage loss 113 Old soil 8 12 40.0 112 New soil 1 19 5.0 The data show clearly that Rhizoctonia persists in the old soil of the benches from year to year. The evidence also seems to indi- cate that the disease becomes more virulent in the soil the second season. INFLUENCE OF MANURES To determine whether Rhizoctonia is introduced in the bench thru the use of manures, comprehensive experiments were carried on dur- ing the seasons 1912-13 and 1913-14, with negative results. Since greenhouse soils receive, previous to the filling of the benches, heavy applications of manures, it is not improbable that such soils offer a good environment for the rapid growth of the fungus and present conditions conducive to its attack on the plant. A compari- son in this respect was therefore made between soils containing no manure and soils receiving applications of different amounts of manures. Eight five-foot sections were filled with soil, manure was added to and incorporated with the soil of six of them, while two 1919] CARNATION STEM ROT AND ITS CONTROL 587 sections received no manure. Each section was inoculated with the fungus by mixing with the soil about a bushel of infected soil taken from benches in the experimental house where plants had previously succumbed to the disease. Twenty-five plants (variety Rosette) were planted in each section and uniform treatment given. TABLE 3. RELATION OF VARYING AMOUNTS OF MANURE IN THE SOIL TO THE VIRULENCE OF STEM ROT: 1914-15 Sec- tion Treatment Number of healthy plants Number of diseased plants Percentage loss 254 255 Check: no fertilizer or manure 20 pounds of manure 22 20 3- 5 12.0 20 256 40 pounds of manure 25 0.0 257 80 pounds of manure 21 4 16.0 258 160 pounds of manure 18 7 28 259 260 Check: no fertilizer or manure 40 pounds of manure 21 25 4 16.0 261 80 pounds of manure 8 17 68.0 The data shown in Table 3 are someAvhat contradictory. On the whole it seems that manure added to soil has little influence on the growth and parasitism of the fungus. COMMERCIAL FERTILIZERS Table 4 contains data of plants growing in soils treated with commercial fertilizers. The sections in the experiment were inocu- lated with the fungus by adding to each a pint of a mixture of sand and corn meal in which the fungus was growing. Twenty-five Rosette carnations were planted in each section. TABLE 4. RELATION OF EXCESSIVE AMOUNTS OF COMMERCIAL FERTILIZERS TO THE VIRULENCE OF STEM ROT IN THE GREENHOUSE: 1914-15 Sec- tion Treatment Number of healthy plants Number of diseased plants Percentage loss 246 Check : no fertilizer 8 17 68.0 247 248 Dried blood 1 pound per week. . Potassium sulfate 1 pound per week 7 18 18 7 72.0 28.0 249 250 251 252 253 Dried blood 1 pound per week and 4 pounds limestone 1 .... Potassium sulfate 1 pound per week and 4 pounds limestone 1 Ammonium sulfate 1 pound 1 . . . Ammonium sulfate 2 pounds 1 . . Ammonium sulfate 4 pounds 1 . . 10 9 14 9 6 15 16 11 16 19 60.0 64.0 44.0 64.0 76.0 limestone and ammonium sulfate turned into soil before setting plants. 588 BULLETIN No. 223 [September, The data do not show any close relation between the use of com- mercial fertilizers and infection. In most cases the commercial fertilizers were used in excessive amounts. This in all probability' had an influence on infection as a whole, for excessive amounts added to soil lower the vitality of the carnation plant. This was noticeable in the sections to which potassium sulfate was added, the plants show- ing the usual symptoms of overfeeding with potassium. The plants of Sections 252 and 253 also showed clearly the effects of the large amounts of ammonium sulfate used. The large application of dried blood in Section 247 showed its effects on the physical structure of the soil and the plants did not make normal growth. The high per- centage of infection in these sections is in all probability correlated with the weakened condition of the plants. Nevertheless, the per- centage of loss in the untreated soils of the check sections was high, so that no definite conclusions can be drawn from the results. ACIDITY AND ALKALINITY OF THE SOIL In 1912 limestone was tested out next to a section in which sulfuric acid was used as a possible control measure. Both of these methods failing as far as control was concerned, the experiments were carried out thru two more seasons to test out the effects of alkalinity and acidity of the soil and its relation to stem rot. A solution of sulfuric acid was prepared and applied to soil of a five-foot section at the rate of three-sixteenths fluid ounce per square foot. One day previous, the soil was inoculated with Rhizoctonia by mixing with it a pint of infected soil. Two days after the acid treatment, the section was planted to twenty carnation plants (variety Beacon) . A second section was inoculated and planted the same as the first, while a third was inoculated and five pounds of crushed lime- stone (applied at the rate of five tons to the acre) was thoroly mixed with the soil two days later. A combination of the acid-limestone treatment was applied to a fourth section. The soil in this section also was inoculated and allowed to stand for a day. The sulfuric- TABLE 5. EFFECTS OF ACIDITY AND ALKALINITY ON THE VIRULENCE OF STEM ROT IN THE GREENHOUSE: 1912-13 Sec- tion Treatment Number of healthy plants Number of diseased plants Percentage loss 109 Sulfuric acid, , 3 8 fluid ounce per square foot . 7 13 65 110 Check 16 4 20.0 111 Limestone 5 pounds 19 1 5.0 119 Sulfuric acid plus 5 pounds limestone 15 5 25.0 1919] CARNATION STEM EOT AND ITS CONTROL 589 acid solution was then applied, and on the second day after five pounds of crushed limestone was mixed with the soil. The results shown in Table 5 indicate that the acid solution did not control the amount of stem rot. Tests made frequently during the course of the season gave good acid reactions. The addition of crushed limestone, however, appears to have checked stem rot. The above experiment, with some modifications, was repeated dur- ing the seasons 1913-14 and 1914-15. For the first season the same amounts of acid and limestone were used, while for the second season, these amounts were doubled. The experiment was divided into six treatments, two five-foot sections being devoted to each treatment. Each section was planted to twenty-five plants (variety White En- chantress) and all given the same conditions thruout the season. Before planting, the sections were treated as follows: Two sections were inoculated with a soil culture of Rhizoctonia, allowed to stand for several days, and then given an application of sulfuric acid at the rate of three-sixteenths fluid ounce per square foot. In 1914-15 this rate was doubled. Two other sections were given an application of sulfuric acid at the above rate, allowed to stand for three days, and then inoculated with a soil culture of Rhizoctonia. The rate of application was doubled in 1914-15. To TABLE 6. EFFECTS OF ACIDITY AND ALKALINITY ON THE VIRULENCE OF STEM ROT IN THE GREENHOUSE: 1913-14 Sec- tion Treatment Number of healthy plants Number of diseased plants Total diseased Percentage loss 167 173 168 174 169 175 170 176 171 177 172 178 Inoculated. Acid treat- ment 5 1 11 24 25 25 1 4 16 25 25 20 24 14 1 24 25 21 9 44 15 49 30 88.0 30.0 0.0 98.0 60.0 0.0 Inoculated. Acid treat- ment Acid treatment. Inocu- lated Acid treatment. Inocu- lated Acid treatment. Check . . . Acid treatment. Check. . . Inoculated. Limestone (5 pounds) Inoculated. Limestone (5 pounds) Limestone (5 pounds). Inoculated Limestone (5 pounds). Inoculated Limestone (5 pounds). Check Limestone (5 pounds). Check 590 BULLETIN No. 223 [September, FIG. 2. VIRULENCE CF STEM ECT IN THE GREENHOUSE IN AN ACID SOIL (Photographed Sept. 20, 1914) Section 236 Inoculated. Acid Treatment Section 237 Acid Treatment. Inoculated Section 238 Acid Treatment. Check 1919] CARNATION STEM EOT AND ITS CONTROL 591 FIG. 3. AN ALKALINE SOIL INEFFECTIVE IN CONTROLLING THE VIRULENCE OF STEM EOT IN THE GREENHOUSE (Photographed Sept. 20, 1914) Section 239 Inoculated. Limestone Section 240 Limestone. Inoculated Section 241 Limestone. Check 592 BULLETIN No. 223 [September, two other sections sulfuric acid was applied at the same rate as above and allowed to stand several days. Six additional sections were treated in the same way as the six sections above, except that the acid treatment was in each case replaced by 5 ^pounds of crushed limestone. In the 1914-15 experiments 10 pounds of crushed lime- stone was used instead of 5 pounds. The results of these experi- ments are summarized in Tables 6 and 7 (see also Figs. 2 and 3). Under the conditions of the above experiments, neither sulfuric acid nor lime had a controlling effect on stem rot. The fungus seemed to thrive equally well in an acid soil and in an alkaline soil. This result has been corroborated by growing the fungus in the laboratory on culture media of definite, known acidity and alkalinity; within certain limits the fungus showed but little preference for either sub- stratum. TABLE 7. EFFECTS OF ACIDITY AND ALKALINITY ON THE VIRULENCE OF STEM ROT IN THE GREENHOUSE: 1914-15 Sec- tion Treatment Number of healthy plants Number oi diseased plants Total diseased Percentage loss 230 Inoculated. Acid treat- ment 6 236 Inoculated. Acid treat- ment 4 231 Acid treatment. Inocu- lated 5 237 Acid treatment. Inocu- lated... 7 232 Acid treatment. Check ... 25 238 Acid treatment. Check ... 25 233 Inoculated. Limestone (10 pounds) 10 239 Inoculated. Limestone (10 pounds) 4 234 Limestone (10 pounds). Inoculated 6 240 Limestone (10 pounds). Inoculated 235 Limestone (10 pounds). Check 25 241 Limestone (10 pounds). Check 25 19 21 20 18 15 21 19 25 40 38 36 44 80.0 76.0 0.0 72.0 88.0 0.0 1919] CARNATION STEM EOT AND ITS CONTROL 593 REPLANTING Experiments were carried on for two seasons to determine what percentage of the plants survived when replanted under ordinary greenhouse conditions. After a large number of plants had been taken out of the different sections in a diseased condition, they were replaced by new plants. As can be seen from Table 8, 68 to 100 per- cent of the replants were killed by stem rot. An average of 92 per- cent for all sections was lost. From these results we can conclude that the mortality of the replants is extremely high and in a few cases only will they survive thru a growing season. TEMPERATURE Cultures of Rhizoctonia in the laboratory have shown that the fungus grows best at a relatively high temperature. The optimum temperature for the growth of the fungus is from 86 to 88 degrees Fahrenheit. This is much higher than the optimum temperature for the growth of the carnation plant. Carnations in the greenhouse are grown, when possible, at 50 to 53 degrees F. at night and 60 to 62 degrees F. during the day. Altho the stem-rot fungus will grow at the latter temperatures, its growth is slow. These facts indicate that there may be a temperature relation between the growth of the parasite and host infection, and that possibly temperature is the controlling factor in infection. Carnation growers probably are aware of the fact that losses due to stem rot are greater at certain periods of the year than at others. The following data, collected during a period of five years, show that this is true. The data also tend to confirm the existence of a more or less definite rela- tion between temperature and loss by stem rot. In Table 9 is given the data of the benching of carnation plants for five years and the subsequent losses of plants by months. For two seasons the plants were benched during September; the following three seasons they were benched in August. From the data presented it is seen that the greater losses occur during the month following that of benching. When benching was done in Sep- tember, no loss occurred during that month, but the greater loss occurred during October. When benching was done in August, the greater loss occurred in September, and the total loss was much larger than among the plantings benched in September. It also is seen from the data that loss gradually decreases from the first month after benching to the beginning of the warmer months of the following season. In Table 8, also, the monthly loss is tabulated, with the same results. During August, September, and October, in the state of Illinois, the outdoor temperature is high and the temperature in the 94 BULLETIN No. 223 [September, H H B O tf o g I o a I 3 as 3T3 i g * St j^ O oooooooooo CD es "-9 oooooo (N >> cj S ooooo ^ a <1 CCOOO-* C a % ooor^o J3 -i c a & r f=H t^oooo >> .Q CO 03 j c3 >-s lOrH(N(N O o Q ^H 00 COIN 1 * i i o 55 (M ICHOOCO +j o "500 CO O Tt< rHr-KNCO"* -tj & OOCOQOO l-H Tt< 3 S 1 CO l> C5 O> CO CO (M <*! OS 00 t4 6 55 3 c3 "& C nl Sec- tion Treatment Gloriosa White Enchant- ress ber dead number dead percent loss 156 161 Inoculated. Sterilized Inoculated. Sterilized 25 25 25 25 157 162 Sterilized. Inoculated Sterilized. Inoculated 25 25 25 25 21 25 1 2 46 3 49 158 Inoculated 25 9 163 Inoculated 25 25 23 8 32 25 25 33 65 159 Sterilized 25 164 Sterilized 25 25 25 160 Check: no treatment . . 25 165 Check: no treatment 25 25 25 1919] CARNATION STEM ROT AND ITS CONTROL 605 TABLE 18. ^RESULTS OF STEAM STERILIZATION IN THE CONTROL OF STEM ROT IN THE GREENHOUSE: 1914-15 Number of plants Sec- tion Treatment Gloriosa White Enchant- tress her dead number dead percent loss 216 221 Inoculated. Sterilized Inoculated. Sterilized 25 25 25 25 217 222 Sterilized. Inoculated Sterilized. Inoculated 25 25 25 25 1 19 10 24 20 34 54 218 Inoculated 25 18 223 Inoculated 25 25 21 22 39 25 25 47 86 219 Sterilized 25 224 Sterilized 25 25 25 220 Check: no treatment 25 225 Check : no treatment 25 25 25 sections in which the fungus was introduced and not sterilized, the losses ranged from 49 to 86 percent (see Fig. 5). Why no losses occurred in the untreated sections is difficult to explain, unless it may be inferred that the fungus was not present in the soil. Records were kept of the production of flowers by the plants in the various sections. These records are given in Tables 19 and 20. In no case was production affected by the soil sterilization process. TABLE 19. EFFECT OF STEAM-STERILIZED SOIL ON PRODUCTION AND QUALITY OF CARNATION FLOWERS: 1913-14 Sections Treatment No. of flowers Perfect Size Stem length Firsts Gloriosa 156, 161 Sterilized No. 584 No. 562 percent 98.2 inches 2.79 inches 17.81 No. 470 percent 80.5 160, 165 Check 579 565 97.5 2.76 17.09 259 44.7 159, 164 Sterilized 568 552 97.2 2.76 17.07 396 70.0 White Enchantress 156, 161 Sterilized. . . . 863 706 81.2 3.11 14.74 758 87.8 160, 165 Check 773 713 92.2 3.12 14.76 643 83.8 158, 164 Sterilized 819 660 81.8 3.11 14.64 637 77.7 606 BULLETIN No. 223 [September, TABLE 20.- -EFPECT OF STEAM-STERILIZED SOIL ON PRODUCTION AND QUALITY OF CARNATION FLOWERS: 1914-15 Sections Treatment No. of flowers Perfect Size Stem leflgth Firsts Gloriosa 216, 221 Sterilized No. 591 No. 577 percent 97.6 inches 2.87 inches 20.53 No. 508 percent 89 3 220, 225 Check 570 533 93.5 2.83 19.73 479 84.0 219, 224 Sterilized 579 563 97.2 2.86 19.12 475 82.0 White Enchantress 216, 221 Sterilized 721 679 94.1 3.18 18.83 701 97.2 220, 225 Check 705 674 95.6 3.16 18.69 674 95 7 219, 224 Sterilized 762 689 90.4 3.09 19.00 737 96.7 CONCLUSIONS AND RECOMMENDATIONS From the data and experimental evidence presented in this bulletin it seems clear that the control of stem rot of carnations lies along the line of careful control of growing conditions of the carnation plant and in the use of a clean ^oil. The disease is a soil disease. The organism lives in the soil, under ordinary conditions as a saprophyte, but under more favorable conditions attacking the carna- tion plant and causing its destruction. The conditions influencing its spread and development are high soil temperature and soil moisture. Soil Disinfectants of Little Value. The results of these experi- ments indicate that the usual soil disinfectants, such as sulfuric acid, lime, Bordeaux, copper sulfate, and formalin, applied to the soil have but little effect on the fungus and that they are consequently of little value as a means of controlling the disease. No chemical solution was found which, when applied to the soil in quantities not harmful to the plant, eradicated the fungus. The fungus is very resistant in soil to weak solutions of acids and alkalies. It is also resistant to low tem- peratures and drying. Evidence is presented that it lives in soils for years, resisting all the rigorous conditions of a cold winter and a hot summer. Steam Sterilization Effective. In order completely to eradicate the fungus from the soil, steam sterilization alone seems to be effective. Dry steam forced thru the soil at forty pounds pressure for one hour will destroy the fungus. There is no indication that such steriliza- tion of soil is accompanied by evil effects on the growth or the pro- duction of carnation plants. Sterilized soil grows equally good carnation plants as unsterilized soil. However, aside from the labor and expense involved in sterilization, unless the plants brought in from the field- are free from the disease organism the disease may again be introduced into the soil of the benches. There is of course 1919] CARNATION STEM EOT AND ITS CONTROL 607 but little assurance that the fungus is not present in the field. In order to prevent the introduction of the disease from the field into the benches, only healthy and uninjured plants should be used. Every plant should be carefully examined at the crown for evidences of the disease and any plant showing symptoms should be discarded. Importance of Low Temperature and Minimum of Moisture. The first month the plant is in the bench is the most critical point in the life of the plant, especially if the transplanting is done early. The temperature of the greenhouse is high at this time, and, still more important, owing to the large amount and the frequent use of water concomitant with transplanting, the humidity of both soil and air is high. Experiments have shown that high temperature and high water content of soil, especially when existing simultaneously, offer a most favorable environment to the fungus. High temperatures in the cutting bench and in the carnation house give Rhizoctonia a two- fold advantage; they lower the vitality of the cuttings and plants and give the fungus optimum conditions under which to develop. In other words, when normal temperature for the best development of the plant is furnished, no stem rot occurs ; while if high temperatures are maintained, the vitality of the plant is lowered, thus making it more susceptible to stem rot. At the same time, high temperatures favor the growth of the fungus, increasing its virulence. A careful watch, therefore, of the growing conditions of the plants is necessary at this time. The temperature should be kept as low as possible and no more water applied to the soil than is absolutely necessary for a healthy growth of the plant. Seedlings and Cuttings. These statements apply also to the grow- ing of seedlings and cuttings. Steam sterilization of soil and sand is recommended whenever it is possible. The cutting bench offers a most favorable environment for the growth of the fungus if it is present in the sand. A relatively high temperature and high per- centage of moisture of the sand, as well as the high humidity of the air resulting from artificial shading, are characteristic of the cutting bench. Under such conditions it is extremely difficult to control damping-off if it is present in the sand. It is therefore recommended that the sand be sterilized with steam and careful attention given later to the moisture and temperature conditions. A relatively high temperature of soil together with a high percentage of moisture is conducive to infection. It is important, therefore, that the tempera- ture be "kept as low as possible for a good healthy growth of the carnation plant. This temperature, since it is lower than that of the optimum temperature of the fungus, will prove an important factor iu the control of infection. AUTHOR INDEX (500 AUTHOR INDEX Bull, Sleeter, Grindley, H. S., Mumford, H. W., and Em- niott, A. D. Fertilizing Con- stituents Excreted by Two- year-old Steers '. . . . 127-162 Bm-lison, W. L., and Stark, E. W. Spring Wheat for Illinois. 313-320 Crandall, Charles S. Apple-Bud Selection : Apple Seedlings from Selected Trees 179-264 Kmmett, A. D., Grindley, H. S., Mumford, H. W., and Bull, Sleeter. Fertilizing Constit- uents Excreted by Two-year- , old Steers .".127-162 Fahrnkopf, H. F. T., Hopkins, Cyril G., Garrett, F. W., and Whitchurch, J. E. Illi- nois Crop Yields from Ex- periment Fields 397-504 Garrett, F. W., Hopkins, Cyril G., Whitchureh, J. E., and Fahrnkopf, H. F. T. Illinois Crop Yields from Experi- ment Fields 397-504 Grindley, H. S., Mumford, H. W., Emmett, A. D., and Bull, Sleeter. Fertilizing Constit- uents Excreted by Two-year- old Steers '.127-162 Grindley, H. S., and Busk, H. P. Field Investigations of For- age Poisoning in Cattle and Horses 161-176 Gunderson, A. J. Field Experi- ments in Spraying Apple Orchards for the Control of Apple Blotch 549-576 Gunderson, A. J. The Pruning of Winter-Injured Peach Trees 381-394 Hopkins, Cyril G., Garrett, F. W., Whitchurch, J. E., and Fahrnkopf, H. F. T. Illinois Crop Yields from Soil Ex- periment Fields 397-504 PAGE Mosier, J. G. Climate of Illi- nois 1-126 Mumford, H. W., Grindley, H. S., Emmett, A. D., anil Bull, Sleeter. Fertilizing Constitu- ents Excreted by Two-year- old Steers 127-162 Pearson, F. A. The Cost of Milk Production Computed on the Year Basis 341-364 Peltier, George L. Carnation Stem Rot and its Control. 577-608 Peltier, George L. Snapdragon Rust 533-548 Rusk, H. P., and Grindley, H. S. Field Investigations of For- age Poisoning in Cattle and Horses 161-176 Stark, R. W., and Burlison, W. L. Spring Wheat for Illinois . 313-320 Stevens, Frank Lincoln. An Ap- ple Canker Due to Cyto- spora '365-380 Stevens, Frank Lincoln. Two Illi- nois Rhubarb Diseases. . .297-312 Stevens, Frank Lincoln, and True, Esther Young. Black Spot of Onion Sets 505-532 Stewart, Robert, and Wyatt, F. A. Limestone Action on Acid Soils 265-296 True, Esther Young, and Stevens, Frank Lincoln. Black Spot of Onion Sets 505-532 Whitchurch, J. E., Hopkins, Cyril G., Garrett, F. W., and Fahrnkopf, H. F. T. Illi- nois Crop Yields from Ex- periment Fields 397-504 Wyatt, F. A., and Stewart, Robert. Limestone Action on Acid Soils 265-296 Yapp, W. W. A Study of the Relative Reliability of Offi- cial Tests of Dairy Cows. 321-340 610 VOLUME 15 INDEX (The headings in capitals are subjects of entire bulletins) PAGE Acidity of soil, influence on car- nation stem rot 588-92 Aledo experiment field, Crop yields in soil experiments. 405, 407 Alfalfa, germination at various temperatures 25 Alkalinity of soil, effect on car- nation stem rot 588-92 Anthracnose, on onion sets 507 Ehubarb 299-308 Anticyclones, Weather changes produced by 5, 9 Antioch experiment field, Crop yields in soil experiments. 406, 407 Antirrhinum ma jus 535, 540,548 Apple blotch Recommendations for control of 575 Spraying for control of 549-75 Weather conditions affecting. . 553 Apple-bud selection Comparative value of buds from different locations on shoot 232-50 from different Ideations on tree 202-31 Comparative value of robust and slender scions 250-52 Conclusions 263-64 Effect of vigor of stock on growth 252 Influence of care in grafting. 252-53 Test of size 183-202 Varietal and individual differ- ences 253-54 APPLE-BUD SELECTION: AP- PLE SEEDLINGS FROM SELECTED TREES .... 179-264 APPLE CANKER DUE TO CYTOSPORA, AN 365-79 Bibliography 377-79 Description 367-68 Fungus 368-72 APPLE ORCHARDS, FIELD EXPERIMENTS IN SPRAYING, FOR CON- TROL OF APPLE BLOTCH 549-75 Apple seedlings, tests with, from selected trees 254-64 Black spot of onion sets 505-32 See also Onion sets PAGE Bloomingtou experiment field, Crop yields in soil experi- ments 408,410 Blotch, Apple, see Apple blotch Calves, Tests to determine feeds responsible for unthriftiness of 165-67 Carlinville experiment field, crop yields in soil experi- ments 409,410 CARNATION STEM ROT AND ITS CONTROL 577-607 Carnations Branch rot 583 Stem rot Conditions influencing growth of parasite and host. . . .58497 Control of 599-606 Conclusions and recommen- dations 6'06-07 Fungus 585-86 Carthage experiment field, Crop yields in soil experiments. 411, 413 Cattle, Feeding tests for forage poisoning of 163-69 See also Dairy cows, Steers Chicago, Cost of milk production for 344-64 Clayton experiment field, Crop yields in soil experiments. 412, 413 Cleistothecopsis circinans .... 507, 530 CLIMATE OF ILLINOIS 1-125 Clover, Red, germination at var- ious temperatures 25 Colletotrichum erumpens .... 299-308 Colletotrichum, Falcate-spored forms of 307-08 Corn Days required for germination at various temperatures 25 Effect of rainfall on yield 28-30 Temperature for growth 27 Corn silage, see Silage Corticium vagum 579 Cows, see Cattle, Dairy cows Cutler experiment field, Crop yields in soil experiments . 41416 Cyclones, Weather changes pro- duced by 5, 9 Cytosporas Bibliography 377-79 on Rosaceous hosts 374-75 INDEX 611 PAGE DA1HY COWS, A STUDY OF THE RELATIVE RELIA- BILITY OF OFFICIAL TESTS OF 321-39 Dairy cows Official tests Comparison of seven-day test and seven-day test eight mouths after calving. . .334-36 Comparison of seven-and thirty-day tests 333-34 Conclusions .'539 Correlation between semioffi- cial and 337-38 Explanation of 323-24 Plan of investigation 325 Records 324-2.1 Relation of fat percentage to test period 327-28 Variability in percentage of fat 330-32 Semiofficial tests Accuracy 325-27 Correlation between seven- day and 337-38 Explanation of 324 Relation of fat percentage to test period 328-30 Variability in percentage of fat 332-33 Used in tests 323 Dairying, see Milk production DeKalb experiment field, Crop yields in soil experiments. .417-19 Variety tests of spring wheat 318,319 Dixon experiment field, Crop yields in soil experiments . 420-22 Drainage, Effect upon loss of limestone from soil. . .272-73, 293 Dubois experiment field, Crop yields in soil experiments . 423-24 Dusting apple trees for control of apple blotch 551, 552 Compared with liquid spray- ing 568, 569 Edgewood experiment field, Lime- stone on 267-68 Enficld experiment field, Crop yields in soil experiments.425, 427 Experiment fields, see Soil experi- ment fields, names of particu- lar fields lowing experiment field, Crop yields in soil experiments . 426, 427 Fairfield experiment field, Crop yields in soil experiments. . .428-30 Fertilizers 402-03 Commercial, Influence on car- nation stem rot of 587-88 PACK Manures, Influence on carna- tion stem rot of 586-87 Commercial value of. .15559, 354 FERTILIZING CONSTITU- ENTS EXCRETED BY TWO-YEAR-OLD STEERS 127-62 Flax, germination at various temperatures 25 Flora, 111., Spraying experi- ments 553-75 FORAGE POISONING IN CAT- TLE AND HORSES, FIELD INVESTIGATIONS OF.. 163-76 Serum developed 171 Serum treatment ..171-72,174,175 Friend spray gun 571 Frost, Time of, in Illinois 46-47 Fungicides, Experiments for con- trol of snapdragon rust.. 541-44 See also Sprays Galesburg experiment field, Crop yields in soil experiments. 43 1-34 Grafting, Influence of care in. 252-53 Grain system of farming on ex- periment fields 401-02 Harristown, 111., Feeding test with suspected silage at. . .168-69 Hartsburg experiment field, Crop yields in soil experiments. 435-36 Holstein-Friesian dairy cattle used in tests 323 Horses, Forage poisoning investi- gations 169-75 Serum treatment . . .171-72, 174, 175 Illinois, Climate 1-125 ILLINOIS CROP YIELDS FROM SOIL EXPERI- MENT FIELDS 397-503 Joliet experiment field, Crop yields in soil experiments. 437-38 Kewanee experiment field, Crop yields in soil experiments. . . .439 Lamoille experiment field, Crop yields in soil experiments. 440-41 Lebanon experiment field, Crop yields in soil experiments . 442-44 LIMESTONE ACTION ON ACID SOILS 265-96 Results from Newton field . . 268-85 Results from Odin field 286-95 Limestone Comparative effect of light and heavy applications. . 286, 288, 291 Comparative value of high-cal- cium and dolomitic 274-80 Effect of degree of fineness. .280-82 Effect of drainage upon loss of 272,293 612 YOM'MK 1") PAGE Effect on surface soil 270 Influence on subsurface and subsoil . ...273-74,282-85,291-93 Live-stock fanning on experiment fields 401 McXabb experiment field, Crop yield in soil experiments. 445, 447 Manure, see Fertilizers Motor iological summary, 111. Exp. Sta. (1889-1916) * 55-64 MILK PRODUCTION, COST OF 341-64 Bases of calculation 344-45 Conclusions 364 Cow as unit in determining. 357-64 Expenses 360-64 Xet cow cost 362-64 Returns 362-63 Dairy herd as unit in determin- ing 346-57 Expenses 347-52 Net herd cost 354-56 Returns 353-54 Farm as unit in determining. 345-46 Source of data 345 See also Dairy cows Minonk experiment field, Crop yields in soil experiments . 446, 447 Mold on onion sets 507 Morrow plots 401 Crop yields in soil experi- ments 486-87 Mt. Morris experiment field, Crop yields in soil experiments. 448-49 Xeck rot of onion sets 507 Xeoga, 111., Experiments with winter-injured peach trees. 386-87 Xewton experiment field, Crop yields in soil experiments. .450-54 Limestone experiment on ... .268-85 Xitrogen excreted by steers. . .143-50 Oats, germination at various tem- peratures 25 Oblong experiment field, Crop yields in soil experiments . . . 455-56 Odin experiment field, Crop yields in soil experiments 457-61 Limestone experiments on ... 286-95 Olney, 111., Experiment with win- ter-injured peach trees. . .387-93 OXIOX SETS, BLACK SPOT OF 505-32 Bibliography 532 Causal fungus 509-11 Control of 531-32 Morphology 529 Perithecium 511-12 Taxonomic position of asciger- ous stage 529-30 Type of disease 508-09 PAGE Oquawka experiment field, Crop yields in soil experiment. .462-63 Ottawa, 111., Forage poisoning in- vestigations at 169-76 Pana experiment field, Crop yields in soil experiments 463-65 PEACH TREES, THE PRUN- ING OF WINTER-IN- JURED 381-94 Phosphorus excreted by steers . 150-55 Phyllosticta straminella 308-312 Poff Orchard, experiments at.. 387-93 Pumpkin seed, germination at various temperatures 25 Rainfall in Illinois 10-22, 55-64, 65-119 Raleigh experiment field, Crop yields in soil experiments . 466-67 Rhizoctonia, Temperature best for growth of culture 593 EhizoctontO' Solani 579 Rhubarb Anthracnose 299-308 Fungus 300-05 RHUBARB DISEASES, TWO ILLINOIS 297-312 Rhubarb leaf spot 308-12 Fungus 310-12 Rockford experiment field, Crop yields in soil experiments. 468-72 Rosaceous twigs, Fungi on. . . .372-75 Rye, germination at various tem- peratures 25 Seedlings, Experiments with ap- ple 254-64 Sidell experiment field, Crop yields in soil experiments . 473-74 Silage, Feeding tests with sus- pected 163-69 Smudge on onion sets 507 SNAPDRAGON RUST 533-48 Control ,. .541-47 Fungus, Description of 538 History and distribution. . . .535-36 Host relationship and resis- tance 538-41 In the field 547 Prevention and control 541-47 Recommendations 548 Seed not carriers of 546-47 Summary 548 Symptoms 536-38 Snowfall in Illinois 22-24 Soil Disinfection of 599-602 Limestone action on acid . . . 265-96 Moisture affecting carnation stem rot 595-97 Steam sterilization 602-06 Temperature of. ... 42, 43, 44, 45, 46 IXUEX 613 PAGE Soil experiment fields Illinois crop yields from. . .397-503 List of 399,503 Materials for soil treatment .402-0:? Rotations 401-02 Systems of farming 401-02 Sparta experiment field, Crop yields in soil experiments. .47576 Spraying experiments for control of apple blotch . . 549-75 Dusting and liquid spraying compared 568,569 Incidental observations .... 561,570-71,573,575 Objects 551,561 Recommendations 575 Summary of results, 1916. . . .560 1917 570 1918 573 for control of snapdragon rust 541-44 Sprays for apple trees Arsenate of lead 551, 552 with lime sulfur .568, 569 Bordeaux 551 Formula 552 with lime sulfur, see Sprays for apple trees, Lime sulfur Copper sulfate . . .551, 552, 562, 563 Lime sulfur 551,552,562,563 arsenate of lead 562, 563 copper sulfur mixture. . .562, 563 Lime sulfur and Bordeaux Effect of interchanging. .559-60 Relative values 553-55, 563-65, 571-73 Value of different applica- tions ..555-59,565-68,573,574 Scalecide 551, 552, 562, 563 Spring Valley experiment field, Crop yields in soil experi- ments 477 Steam sterilization for control of carnation stem rot 602-06 Steers, Experiments to determine fertilizing constituents ex- creted by two-year-old .... 127-62 Conclusions 161-62 Equipment and methods of ex- periment 131 Feces Amount 133-34 Chemical composition. . . . 135, 136 Feeds Amount 132-33 Composition 133 Cost 157 Rations 129-31 Financial statement 155-59 Nitrogen excreted 143-50 PAGE Organic matter consumed 141, 143 excreted 138-40, 141, 142 Phosphorus excreted 150-55 Summary 159-61 Urine Amounts 136-37 Collection and sampling.... 131 Composition 136, 137-38 'Stem rot, Carnation, sec Carnations Sunshine, average amount for Illi- nois 51 Syringing, Effect on snapdragon rust of 545-46 Temperature of Illinois 25-46 Meteorological summary (1889- 1916) 55-64 Records 121-25 Timothy, germination at various temperatures 25 Toledo experiment field, Crop yields in soil experiments. 478-79 Union Grove experiment field, Crop yields in soil experi- ments 480-82 Unionville experiment field, Crop yields in soil experiments. 483-85 Urbana, Variety tests of spring wheat 317,319 Urbana experiment field, Crop yields in soil experiments. 486-97 Valsas on fruits 376 on Rosaceous hosts 372-73 Vermicularia cirdnans. . .507, 529, 530 V ermiculariose on onion sets 507 Virginia experiment field, Crop . yields in soil experiments.498-500 Volutella circinans .507-32 Volutella, Falcate-spored forms of 307 Voris Orchard, experiments at. 386-87 Weather affecting apple blotch 553 maps . . 6, 7 See also Climate West Salem experiment field, Crop yields in soil experiments. . .501-02 Wheat, germination at various temperatures 25 WHEAT, SPRING, FOR ILLI- NOIS 313-20 Culture 315 Drills 316-17 Time to sow 315-16 Variety tests 317-18 Yields and value 318-20 Wind in Illinois 48-50,55-64 Winter injury to peach trees. .383-94 UNIVERSITY OF ILLINOIS-URBANA