#f.s:/jr U.S. DEPARTMENT OF AGRICULTURE DIVISION OF i WTO MO LOOT. rtS» Bulletin No. 15. —w T 1 1 i : JUN i960 ICKRYA OH FLUTED SCALK. tn iikuu isk know n v- rnr. COTTONY CUSHION-SCALE. [REPRINT OF BOME RECENT ARTICLES B OP A REPORT FROM I'ili: AGRICULTU STATION, l'M\ ERSITY WASH I ffGTON: GOV R R N M E N T PRINTING I F 1887. U.S. DEPARTMENT OF AGRK ULTURE DIVISION OF ENTOMOLOGY, BULLETIS Ni>. 15. T i i i •: [CERYA OK FLUTED SCALE, OTIIEP.WI COTTONY CUSHION-SCALE. [REPRINT OP SOME RECENT ART] LES BY I IE ENTOMOLOGIS'I \M> OP A REPORT FROM THE A. KM II. I ITR \l. i XP1 RIMES I STATION, UNIVERSITY OF ( ILIFORNIA.] WASH1 X Q TON: OOVKBN3J E N T 1'KIM 1 887. inj—l'.iill. 15 (M> XT KXTS. P«Jte- Letter of Submittal 6 I nt roil net ion 7 Tin- Boale- insects of the Orange in California, and particularly the loeryaor riiiti a Boale, A. 9 Not i a on ;, i r\ i Its probable Origin the Islands of Bonrbon ami Mauritius. . . 87 TheUw - - :'>."> LETTER OF SUBMITTAL DEPAB l Ml'.N I OB Ageiculi cke, Division op Entomology . Washington, I>. C, June 27, 1887. Beb l have the honor to submit for publication Bulletin No. 15, from this Division, prepared under yonr instructions. Respectfully, C. A'. RILEY, Entomologist. HOO. NoKMAN J. Col. MAN. Commissioner of Agriculture. 5 Digitized by the Internet Archive in 2013 http://archive.org/details/iceryscOOusde [NTRODUCTION This Bulletin consists, 1st, of n reprint of an address delivered at Riverside, Gal., on the treatment of Scale-insects, and more particu- larly <>f the [cerya of the Orange, known variously as the "Australian Bug," "Cottony Cushion-scale," "White Scale," "Fluted Bcale," &c; 2nd f a subsequent communication as to its possible origin and sj cony my; 3rd, b recent important bulletin from the State University of California on the use of gases against Scale-insects. These papers need no further introduction and are all supplementary to an extended article upon the [cerya, which will appear in my annual report. The importance of this insect and of all the different scale-insects af- fecting the Orange in California is such as to justify the republication of these papers, as there is a cbnstanl demand for copies of them. The report by Professor Morse on the useof gases is a valuable contribu- tion to the advancement of our knowledge and means of protecting trees from these scale-insects. It may he looked upon as a direct outgrowth of the experiments made for the Department by -Mr. 1). W. Coquillett, as he bad just begun to experiment with gases whan bis commission ended for want of funds. Be subsequently continued these experiments in a private capacity with more or less success, and that which Professor Morse found most satisfactory is, I believe, essentially the same as that previously adopted by .Messrs. Coquillett, Craw, and Wolfskin ami referred to in my Riverside address. What i> said in that address under the head of "Fumigation" will, neverthel. bold true, no matter how satisfactory the use of these gases may become, and Professor Morse's experiments rather confirm the difficul- ties which I have indicated in the way of producing a gas which will destroy the [cerya and its eggs, as also the danger attending the use of any poisonous gas ami the greater expense attending the use of gases, as compared with washes, especially for those who have few t;. to treat. Some excellent improvements have been made in the cyclone nozzle, whether for facilitating the change of direction or amount of spray, or whether for ease of cleansing, ami I would especially call at- tention to those of John Croften and L D. Green, of Walnut Grove, CaL, and of Vermorel, of Prance. \- Vermorel's arrangement for cleansing i^ as yet unknown in this country, we may briefly describe it as follow. : The nozzle is pierced below by a circular orifice of from live to six; millimeters in diameter, which can be closed by a llyvalve. The n _ 7 alating fliers of the valve project on the outside of the apparatus: In the middle of the valve a needle is welded which occupies the axis of the cylinder, and which, when the valve is raised, may be lodged in the aperture with which the stopper of the cylinder is provided. In this way, when the valve is raised up and the lower orifice unmasked, the upper orifice is closed by the needle. When, on the contrary, the valve closes the lower orifice, the aperture of the stopper is uncovered and allows the liquid to pass out. C. V. R. THE SCALE-INSECTS OF THE ORANGE IN CALIFORNIA. AND PAR- TICULARLY THE ICERYA OR FLUTED SCALE, ILIJS WHITE SCALE. IUJS COTTONY CUSHION-SCALE. ETC. [Address bj Prof. C. V. Rilej before the California State Board of Horticulture, .it Its semi-annual session al Riverside, Cal., April 12, 1887, as reported in the Pa- . iHo Sural Press, April 23, 1881 Afternoon session. The convention met in the afternoon ;it the Pavilion. Lt being cus- tomary to appoint from the fruit-growers al large two honorary vice- presidents ;it each meeting, L. M. Holt, of the Riverside Daily Press, ami s. c. Bvans, of Riverside, were elected to till those positions. Mr. B.M. LeLong, of Los Angeles, was invited to act as assistant secretary. The organization having been fully effected, Mr. Cooper, the presi- dent, gave a brief Btatement of tln> work of the board since its organ- ization. Be referred to its previous sessions, and stated that it was the expressed wish of prominent fruit-growers of Los Angeles that its next session be held eitherinSan Diego, Santa Barbara, or Riverside. He bad accordingly, in the hope that the well-known interests of the people of this section in horticulture would lead to u better attendance than was sometimes obtained, arranged for the meeting bere. The previous session had brought out valuable information, which was being printed, and would be distributed. It was necessary that the mass of new- comers to this portion of the State should be furnished tacts which mighl save them from making expensive blunders. The insect pests are not being overcome as could be wished. He referred to the presence of Professor Riley, one of the most prominent entomologists iii the conn- try, and stated that he would give us Borne valuable information at a Bnbsequent session. He urged co-operation among fruit-growers, and hoped an effort would be made to modify the effect of the interstate commerce bill. The president then introduced Mr. II. .1. Rudisill, a prominent hor- ticulturist of Riverside, who gave an eloquent and verj appropriate address of welcome. At the conclusion of this address the secretary read a well-written and valuable essay prepared by Mrs. 11. ll. Berger, of San Francis on Japanese fruits. 10 At the conclusion of the essay, Mr. Wilcox, of Santa Clara, suggested that the convention consider the points in Mrs. Berger's paper, and re- ferred to the high character of our fruits exhibited at New Orleans, making special mention of the persimmons there exhibited. They could be grown successfully over the larger portion of the State, and were really a very flue fruit. Mr. Klee spoke of the fact that most of the Japanese persimmons were grafted on inferior stock, but that we have a better stock upon which to graft in the European persimmon, and that with it we may expect an improvement in the fruit. He had an idea that while the persimmon would grow well in all sections, it would do better in the more humid portions of the State. He suggested that it would be well to experiment with the Japanese oranges in Eiverside. Didn't think they would grow of large size, but had excellent points in their favor. Mr. Klee said the loquat could be grafted on the quince, but did well on its own root. Said the Chinese had better varieties than those with which we are familiar. This fruit could be dried like the fig. Mr. Starr, of Lugonia, said the persimmon did excellently in the sandy soil of his neighborhood, bearing freely and regularly. Mr. Holmes thought experience in Eiverside had demonstrated the correctness of Mr. Klee's theory that a more humid climate was prefer- able for this fruit, although it fruited satisfactorily here. Tuesday'* session. The convention assembled at 9.30 a. m. The first business on the programme was the address of Professor Riley on Scale-insects. He was introduced by President Cooper in a very off-hand but happy and ap- propriate manner, alluding at some length to the efficient manner in which the professor had conducted the labors of his office, in studying the habits of some of the most destructive insects which have afflicted the firmer and horticulturist, and in devising ways and means to get rid of them. The professor, on taking the floor, very modestly disclaimed the eu- logy which the president had pronounced, and proceeded at once with his address, which was full of valuable information, and which, though quite lengthy, was listened to with the most marked attention through- out. Professor Riley said : Mr. President, Ladies, and GENTLE^rEN : When I left Washing- ton it was with the intention of resisting all invitations to speak, as 1 have been suffering for some time from the effects of overwork and de- sired quietly to pursue some investigations in relation to insects in- juriously affecting fruit culture here and at the same time get rest from exacting office duties. But it was impossible to refuse the urgent appeal of your president, Elhvood Cooper, to address this meeting. I have, however, no formal address to offer you. 11 Tin' subject announced, uamely, •• Entomology in its Relation t" I l"i tirnltiiii'." is one chosen by some enterprising member of your Board, Mini is altogether too comprehensive t . > be dealt with without more time and more thought than 1 have had .it ooi and. I shall endeavor to en: i line m\ remarks t<> scale-insects, and particular! j to what you know as the White Scale. This is the insect which undoubtedly most con cerns you just now, and I have au elaborate article upon ii uov. going through the press at Washington. This, however, would require two or three hours to read, and 1 will pass over the purely historical and entomological details and touch only upon Buch points as will probably interest you. NOMENCL \ I t RE. There is no doubt whatever about this insect beingthe Tceryapur- clmsi, of Masked, and its scientific name is, therefore, fixed." In refer, ence to its popular name, there are several in use, and as between "Australian Bug," ••White Scale," and ••< lottony Cushion-scale" there is \ ery little choice, and it is. as a rule, useless to endeavor to change pop- ular names thai have once come into vogue. So far as they can be changed, however, and with a view of inducing unanimity in the adop tion of a single name, it were better to reject all these names and call it the Fluted Scale. There are mans Australian bugs ami many white scales, some of which, belonging to the genus I'lilrnuiiin. equally well deserve that cognomen. Cottony Cushion-scale is both too long to be acceptable ami would likewise apply to the species of this last genU8 whereas no scale-insect injurious to fruit or Other trees, at present existiug in this country, secretes its white, waxy matter in such a per- fectly fluted mass as this. The generic term, Ecerya, it" once popular- ized like Geranium, Phylloxera, &&, has the advantage of brevity ami still greater accuracy. GEOGR LPHK W. DISTBIBTJ HON. Historical evidence all points to Australasia as the original home of this insect, ami its introduction from Australia to New /calami. Cape Town, South Africa, and California. Nothing was known or published upon the species prior to the seventh decade of this century, and it seems to have first attracted attention almost simultaneously in Australasia. Africa, and America. The evidence as to whether it IS indigenous to Australia or New Zealand, or to both, is not yet satisfactory. Theflrel personal knowledge winch I had of it was from specimens sent to me in 1872 by Mr. B. II. Stretch, then living in San Francisco, ami all the evidence points to its introduction into California by the late ( ice Gordon, of Menlo Park, about the year 1868, and probably from Aus- tralia, on Acacia lati/olia. * This statement is. of course, based on the assumption thai Haskell's pwrdu good species. It may yet j.r" synonym ofsooesaH Bignoret. 12 .More light is, however, yet needed on this point, as in a recent letter received from Baron von Miiller, of Victoria, he claims that it could not have been imported on Acacia into this State, ;is all the Acacias in the State have been grown from seed. This is a matter noon which I should like to have definite information from members of this body, if such information is extant. It is at present widely distributed in the State, and a very full ac- count of its distribution kindly furnished to me by Mr. Matthew Cooke shows that there are some ten infested districts, namely, six in the coun- ties of Marin, Sau Mateo, Santa Clara, Sacramento, Sonoma, and Napa, and four in the counties of Santa Barbara and Los Angeles. I find that it has also obtained a foothold in a few isolated places around San Diego, from which it may yet be stamped out. FOOD PLANTS. A very long list of plants might be enumerated upon which this in- sect is either found accidentally or upon which it can live more or less successfully. But the list of plants, especially of trees important to us for their products, which are seriously affected by it is comparatively limited, and will include the Acacias, Lime, Lemon, Orauge, Quince, Pomegranate, and Walnut. Some few other trees might be added, and it is particularly partial to the Bose and the Nettle ; but it is doubtful whether the species could permanently thrive and multiply to an inju- rious extent on many other trees than those mentioned. CHARACTERISTICS OF THE INSECTS. The genus Icerya was founded by Signoret, a French entomologist, in 1875, being based upon the single species, Icerya sacchari (Guerin), which lives on sugar-cane in the island of Bourbon. This species and the one we are now dealing with are the only two species of the genus, and the diagnosis as given by Signoret, and subsequently elaborated by Masked, of New Zealand, is incomplete and does not include the characteristics of the male. In the report already alluded to I have given a very full character- ization of the species in all conditions and stages, but the only facts that I need draw attention to on this occasion are, first, that the female undergoes three molts and the male two; i. e., each has one more stage than has hitherto been recognized by entomologists and ob- servers; secondly, that it differs from all other members of its family (Coccidae) in its extended powers of locomotion in most of its stages; in its extreme hardiness or power of surviving for a given period with- out food, and in its polyphagous habit, or the ease with which it accom- modates itself to so great a variety of plants. These are the three char- acteristics which most concern you as fruit-growers, and which make it one of the most difficult species to contend with. L3 modi: OP BPRR \l> \nm DISTBIB1 I [ON. All young Boale-insects are qnite active when the) Aral hatch, and most of them al this time are extremelj small, and when \.\ the agency of wind, by running water, or by birds or other insects. Another local means of transport not to be ignored, id upon the clothing of persons engaged in cultivating, upon packages, and upon ;ill implements used, whether in cultivating or harvesting the crop. This particular species also has quite a habit of crawling over the ground, and its local spread is verj matei ially enhanced thereby. It is carried long distances, however, chiefly bj high winds, birds, ami commerce, and its introduction from one continent to another lias undoubtedly Itch effected by the latter method upon young trees or enttings. N \ 1 1 i:ai. enemies. No bird is known yel to attack this insect in California, and l>ut one is mentioned even in Australia, and that upon very slight evidence Of predaceous insects, a Bpecies of Lice wing (genus Chrysopa) has been observed to feed upon it, as also the Ambiguous Lady-bird i Hippodamia (iDihii/iiii). The larva of a little moth, which I have described as Bias tobtuis iceryteella, is also known to teed upon the eggs. Among the Heteroptera, or true bugs, quite a number have been found upon the trees infested with the insect, lnit none have yet been noticed to feed upon it. The most important of its insect enemies an- a Bpecies of ear- wig not yet identified, and a number of mites not yet carefully studied. Of true parasites, none have hitherto beeu rep »rted, whether in Aus tralia, Africa, or America, but 1 aai -lad to announce that two speci- mens of a minute ( 'halcid-tly have been bred by me from specimens around Los Angeles, ami will be described by m\ assistant, Mr. L. <>. Howard, who makes a specialty of the family, under the name of Is,„l,-i>. 7)ius icrti/ir. The genUS is new to our fauna, and the probability is that this little friend was introduced from Australia with its host PBBYENTIYE MBASUEES. Most of the members of this society are doubtless aware that for some four years I was conducting a series of very careful experiments with a view of controlling the scale insects and other insect DfiStS that injuriously affect the orange trees in Florida. This work was carried • Mr. 1'. W. Coqnillett informs me tli.it In- has Bince reared i Pro trotrnpid, proba- bly of tin- genu9 Cotmoooma, from tin- male pnpa. 14 on through the instrumentality of Mr. II. G. Ilubbard, and the Depart- ment of Agriculture has published a special report prepared by him upon this subject. All that is said in that report in reference to the value of preventive measures against the scale-insects of that part of our country will apply with equal force here in California. The value of cleanliness; of thorough cultivation; of pruning judi- ciously so as to get rid of all dead wood, open the top of the trees to the light and to the sun, and facilitate the spraying of the trees need scarcely be emphasized. There may be some difference of opinion as to the value of pruning, while different kinds of pruning, or no pruning, will have their advocates here as they have had elsewhere. The orange makes, naturally, a very dense head, and in the moist climate of Flor- ida, where they have a much larger average of shade, cloudiness, and moisture than you have here, judicious pruning has all the advantages stated, and whether needed or not in California for the purpose of more fully ripening and maturing the fruit, I am quite satisfied from what I have seen that it is just as much needed to facilitate proper spraying of the trees and to prevent overproduction. Some years ago, and prior to the discoveries resulting from the in- vestigation in Florida just referred to, the inadequacy of most washes caused many of the orange-growers of that State to cut back their trees most rigorously, leaving little more than the maiu trunk, in tiie hope of thus being able to kill out or exterminate the scale-insects that troubled them there. I find that many of your orange-growers are going through the same sad experience and resorting to the same sad means. It is a pity to find men thus re-enacting a farce which has been proved in au- other part of the country to be quite unnecessary. Such wholesale lop- ping of limbs requires much labor, and even with the greatest care, which is seldom bestowed upon it, the tree receives an immediate and material injury, and is destined to suffer still more in years to come. Moreover, this radical means ofteu proves futile so far as the results aimed at are concerned, and unless the greatest precaution is taken to properly cover and heal the stumps and to absolutely kill all the iusei ts upon the remaining trunk, as well as those upon the severed branches and the ground, the new growth will soon be as effectually infested as was the old. Many of your own growers have thus lopped or are now cutting back their trees in a very blind way and without the precautious here indicated, on the popular but erroneous supposition that without such precautions they will get rid of the troublesome scales. The value of shelters in the form of surrounding trees and wind-breaks is, I am sure, just as appreciable here, if not so much to protect from frost aud winds, fully as much to protect from infection from scale-in- sects. A row or tall hedge of coniferous trees, such as your cypress, upon which the scale-insects will not thrive — or, better still, a belt of the same — will ofteu serve as an effectual screen to prevent the young insects from being carried from an infested to an uninfested grove. 1") Preventing iU Introduction. — Bat, before passing this Babjecl of pre- ventive measures, I must not omil the importance of anj effort looking to preventing the introduction of this insect from one section of the country or from one neighborhood to another. No Insects bo easily bear transit as these scale insects, and it is eminently true of this par ticnlar Icerya. All tin- worsl species from which they suffer in Florida bave been in- troduced from abroad. Their Long Scale Mytilaapie gloverii) was in- troduced about the year 1835, their Chaff Scale Parlatoria pergandii) from Bermuda some twenty years later, and then- Bed Scale [Aapidio- tus tinis from Havana in 187& We have already seen how this [oerya was introduced into your State from Australia, ami the next worst species which yon have to deal with, namely, yonr Red Scale {Aspidiotut aurantii), was likewise intro- duced, so tar as the evidence goes, from the same country. To enumerate merely the different species of insects destructive of your fruit interests that have been introduced from other part-* of the COUDtiy or from Other parts of the world WOUld consume too much time, and I cannot attempt to do so. Hut I would lay stress upon this con- viction, which has forced itself upon me after a pretty extended experi- ence in all parts of the country, namely, that however much you should encourage all co-operative efforts to prevent such transferring and spread of injurious pests, they cannot he fully exterminated when once they obtain a foothold, and in the end each individual fruit-grower must depend on his own efforts. REMEDIES. It follows without saying that what we should seek in any direct remedy is, first, perfect killing power, or, to he more exact, perfect in- secticide quality associated with harmlessnc>> to the tree; second, reasonable cheapness. Different Washes. — I will not detain you with any general remarks on the subject of insecticides, because it has received full attention in my official reports. Dry insecticides have been found, in the main, unavail- able here, and we must depend upon washes or materials in solution that may be sprayed upon the tier. Here, again, I would remind you of the careful and extended experiments made by Mr. Hubbard in the orange groves of Florida with a view of solving the important question as to what is, on the whole, the most satisfactory liquid application, cheapness and efficiency considered. Carbolic acid, creosote, sulphur- ated lime, silicate of soda, sulphuric acid, sulphuret of iron, bisulphide Of carbon, and many other materials ha ve been thoroughly tried, as well as whale oil soap, potash ami soda lye and their various combinations ; but in the end nothing proved equal toetnulsilied kerosene. Whale-oil SOap is an excellent wash for destroying some insects upon some plants. but it fails to kill theejrgs of our scale insects, so that, however good it 16 may be for scrubbing bho trunks and branches of a tree, I cannot con- scientiously urge it as, on the whole, satisfactory, particularly as it is known to stain the fruit, ami because of the many different grades, varying in their effect and in their value, which are upon the market. Tot ash and soda lye injure the tree more than kerosene does and do not destroy the insects as well, admirable though they are as washes in weaker solution for some other purposes. The action of sulphurated lime (Mowers of sulphur boiled in milk of lime) is very similar to that of caustic potash. Nor withstanding the kerosene emulsions, in proper proportions, have proved so satisfactory against the scale-insects of the Orange in Flor- ida, they have. as a rule, failed to win the good opinion of the orange- growers in California. I have always believed the want of success in this State with the kerosene emulsions was due to imperfect preparation of them, or to imperfect application. I was inclined to give some cre- dence to the theory advanced by my old-time friend, Prof. E. W. Ilil- gard, who is so keenly alive toeverything that interests you, and whose services have been so invaluable to the agriculture and horticulture of the State, namely, that the dryness of the atmosphere in California induced a more rapid evaporation of the kerosene, which may partly account for the difference iu experience betweeu the Atlantic and Pa- cific. For these reasons I had long desired to make a series of ex- periments in California, and finally, last year, did have such a series carried on by Messrs. D. W. Coquillett and Albert Koebele. It were difficult to find in the whole State two gentlemen combining in the one instance more care and reliable entomological capability, and in the other more industry, earnestness, aud euthusiasm. and this I say without desire to flatter, but as evidence that their experiments, so far as they went, were trustworthy — in fact, I may say, the most careful and thorough that have hitherto been made. These experiments ex- tended over a period of three months in the spring and three months iu the autumn, and the detailed reports which these gentlemen have made will be published in connection with my forthcoming annual report. Thej r show that the kerosene emulsions must still be placed at the headol the list of washes, not only for ordinary scale-insects, but for thislcerya or Fluted Scale. Among the different substances thoroughly experi- mented with were caustic potash, caustic soda, hard and soft soaps, to- bacco, sheep dip, tobacco soap, whale-oil soap, vinegar, Paris green, resin soaps and compounds, and so on. It is impossible to give even a digest of the very many experiments, and the varying results obtained with the different washes. It suffices to say that the kerosene emulsion diluted with from eight to ten parts of water was found to kill all the eggs as well as the old females, and that, even when used still stronger, it left the tree uninjured. Mr. Coquillett reports with reference to the much-praised caustic soda, that it has no effect on the eggs of this scale even when applied so stroug as to burn the bark and kill all the leaves. 17 Similarly, the whale-oil soap does ool kill the eggs directly, though it may harden the egg mass bo as to prevent the batching of a large pro- portion of 3 onng Ian a-. R< tin 8oap$. — Mr. Koebele experimenting through August, September, ami October, found aimilarlj good results from the kerosene emulsion, Inn that the crude petroleum, although much cheaper, was more apt to injure the tree. His attention was, however, directed mainly to the preparation of resiuous noapsand compounds on account <>f their greater cheapness. He succeeded in makings cumber of these mixtures which, when properly diluted) need not cost more than one-hslf to one cent per gallon and which produced verg satisfactory results, killing the bisects or either penetrating or hardening the egg masses so as to pre- vent the hatching of the young. Oneof the most satisfactory methods of making a resin soap is to dissolve one pound caustic soda in U gal- lons water to produce thelye; then dissolve 2 pounds resin and one pound tallow by moderate heat, Btirring in gradually daring the cook- ing one quart of the lye, and then adding water until yon have about 22 pints of a brow n and thick soap. This w ill make I 1 gallons of w asb, costing less thantoim half cent per gallon. There is some alight difference between the expei ience of Mr. Koebele and Mr. Ooquillett as to thf value of soap washes, ami the greater suc- cess which the former had with them as compared with the latter was probably dm- to the tact that his experiments were made during the dry or rainless season. The great point of interest, however, in tin-, experiments is that they confirm in a remarkable manner the experience had in Florida. And I think yon will agree with me that they justify the opinions which 1 have expressed in official writings. Such observa- tions as I have been personally able to make during my brief sojourn among yon have greatly served to coufirm me in those opinions, and While the resin soaps experimented with by Mr. Koebele are a valuable addition to our insecticides for the scale-insects, [ find the experience in Florida repeated here, and all the more satisfactory washes have kerosene as their effective basis. There has been, however, a very it waste in applying it, and it is in this direction that reform is most needed. The fact cannot be too strongly urged that in the case of this [cerya, asof most other orange- feeding scale-insects, it is practically impossible, with the most careful and thorough Bpraying, to reach even one of the myriads on the tree. Some few, protected by leaf curl, bark-scale, oi other shelter, w ill ex ape and wit h their fecund progeny SOOn spread over the tree again if left unmolested. Hence, two or three sprayings, not too far apart, are far preferable to a single treatment, howevei thorough. And this is particularly true of the pest we an- considering, which lives on so many other plants, and which in badly infested gro is frequently found crawling over the ground between the trees. MM— Ball. 15 2 18 Value of Kerosene Emulsion. — It is now the custom to use the time of a team and, say, two men for fifteen or twenty minutes or more, and 30, 40, or 50 gallons of liquid on a single medium-sized tree. In this way the tree is sprayed until the fluid runs to the ground and is lost in great quantities, some growers using sheet-iron contrivances around the base of the tree iu order to save and re-use the otherwise wasted material. Now, however much this drenching may be necessary, or has come into vogue, in the use of soap, and potash and soda washes, it is all wrong, so far as the oil emulsion is concerned, as the oil rising to the surface falls from the leaves and wastes more, proportionately, than the water. The essence of successful spraying of the kerosene emulsion consists iu forcing it as a mist from the heart of the tree first and then from the periphery, if the tree is large, allowing as little as possible to fall to the ground, and permitting each spray particle to adhere. It is best done in the cool of the day, and, where possible, in calm and cloudy weather. There has been no morning since my sojourn among you that I have seen the sun rise in a clear sky. Cloudiness has prevailed for some hours after dawn, and in this regard you are favored, as this would be the time of day, of all others, to spray. Proper spraying, should be done with one-fifth of the time and material now expended, or even one-tenth of that which I have seen wasted in some cases, so that three sprayings at proper intervals of from four to six weeks in spring and summer will be cheaper and far more satisfactory than one as ordinarily conducted. In this particular neither Mr. Coquillett's nor Mr. Koebele's experiments •were entirely satisfactory, as I was too far from the field to permit of the detailed direction necessary. I cannot emphasize the fact too strongly that it is practically impos- sible to eradicate, by any system, every individual iusect and egg upon a tree in one spraying. It is almost futile to attempt to do so. Improved Wash recommended. — Let us now see whether the kerosene emulsion, pure and simple, can be improved upon by the addition of any other material. It is plain to be seen from the circulars and docu- ments, both official and unofficial, that have been published in the State and distributed among you, that, in many cases, the proper use of kerosene has been entirely misunderstood. Having already seen that it destroys the eggs of lcerya only wheu used in the ratio of one part of kerosene to about seven or eight of the diluent, it follows that any lesser amount will give less satisfactory results. Moreover, it is extremely important to prepare the emulsion properly. This has usu- ally been done by the use of milk or of soap, because they are cheap and satisfactory. Raw eggs and sujar, and other mucilaginous sub- stances may be used. Experience has shown that the best pro- portions are two parts of the oil to one of the emulsifying agent, whether milk or soap, i. e., for instance, two gallons of the oil to one of milk or one of the soap-water made by dissolving half a pound of soap in one gallon of water. So long as these proportions are maintained 19 a large quantity can be emulsified :i> rapidly as a smaller quantity, and violent agitation through a Bpray-nozzle al a temperature of 100 . and ,i> frequently described In m\ reports, gives the quickest results. Take, fur instance, the mixture recommended bj your county board of horticultural commissioners. You will find that with the soap and wood potash there are twenty -five parts of the dilnent to one of the kero sene recommended, and there is everj reason to believe that the kerosene in this wash might just as well be thrown away, and that it adds com- paratively little, n' .my, to the efficiency of the wash, at least for the tinted soale. If, on the contrary, we could add to the ordinary emul- sion any materials that would give greater adhesiveness, such an addi- tion will prove an advantage. Bnch we get, to some extent, in the soap emulsion, for which reason it has a Blight advantage over the milk emulsion. And after examining the trees treated with resin washes, 1 am Btrongly inclined to recommend thai these resin washes be need as the diluent to the soap emulsion made after the usual formula. Some- thing similar was tried some years ago by one of my agents in Florida, Mi. Joseph Voyle, who used fir balsam in place of resin, in connection with the oil emulsion, and obtained most satisfactory results. Acer- tain amount of dextrine, or, yet better, flour, if mixed with the wash, would prove valuable for the same purpose. Again, if permanency can i>e given to the effect of a wash bo that the few insects escaping the first application, or which would hatch out thereafter, would Buccumb, such addition would be invaluable : and though the arsenites are, as a rule, effective chieflj against mandibn- late insects, or those which masticate their food in other words. although the action of these poisons is mainly through the Btomacfa . yet I happen to know from experience that they have also a direct effect l>.\ contact. Therefore I recommend, with considerable confi- dence, that in this dilute kerosene emulsion there lie added a small proportion of arsenious acid, say from 2 to to :; ounces to every 50 gal- lons of wash. This arsenious acid may be prepared and added in va- rious ways. Probably one of tin- simplest would be to take half a pound ot arsenic to half a pound of sal-soda, boil this in one half gal Ion of water until the arsenic is dissolved, and mix this with about LOO gallons of the diluted emulsion. A quarter of a pound of London pur pie to 50 gallons of the diluted emulsion, or even a still greater amount, would, perhaps, serve the same purpose ami be less likely to injure the tree. I am aware of the danger of making recommendations that have not yet had thorough trial, but I have already made a lew limited experi- ments ami intend making more) which would seem to justify these, and at all events if care be taken not to use too large a quantity of the ar- senic no harm will result from it. either to the tree or to those who use the fruit. 20 Kerosene is not so cheap as the resin compounds, nor as some of the soap and lye washes, but it has this great advantage, that it can be used in much less quantity. It permits a great reduction in the amount of material and the cost of labor. At the rate of 20 cents per gallon wholesale, the effective wash will cost 2i cents per gallon, and from one to two gallons are sufficient, if properly sprayed, on a medium- sized tree. SPRAYING APPARATUS. Just as there is a great wastage of time and money in drenching a tree with kerosene emulsion, so the spraying nozzle most in vogue with you is also somewhat wasteful. That most commonly used is the San Jose nozzle, in which the water is simply forced through a terminal slit in a narrow and rather copious jet of spray. It is the force and direct- ness of the spray which gives this nozzle its popularity under the mis- taken spraying notions that prevail, and to this I should probably add the fact that, being a patented contrivance, it is well advertised, and on the market, for somehow or other people rarely value a gift as much as what they buy, and too often rate value by price. The Cyclone noz- zle, or Riley atomizer, as it is called in France, which has proved so sat- isfactory in the East as well as to my agents at Los Angeles, hasscarcely had such trial among you, so far as I have been able to see, as to prop- erly impress its advantages. That originally made and sent out by the late G. X. Alilco, of Stockton, was patterned in size and form after one which I sent him, and which was designed to spray from near the sur- face of the ground. What I would use for the orange grove, or for trees, is a bunch of nozzles of larger capacity, the size of the outlet to be regulated by the force of the pump. I have witnessed all forms and sorts of spraying devices, and while there are many that are ingenious and serve a use- ful purpose, I can safely say that there is no form which will produce a spray so easily regulated and altered to suit different conditions, and which is so simple and so easily adjustable to all purposes. Since among you I have endeavored to get a bunch nozzle, such as I would recommend, made at Los Angeles, and the difficulties I have had in get- ting it made properly illustrate, perhaps, some of the reasons why this nozzle has not become more popular on this coast. All the parts must be well fitted ; the inlet must be tangential and the outlet so made as not to overcome the whirling or cyclonic action of the water. The breadth, directness, force, or fineness of the spray are all regulated by the form and size of the outlet, and if a thick cap be used it must be gradually countersunk on both sides until the thickness at the outlet does not exceed one-sixteenth of an inch or less. A bunch of four noz- zles, one arrauged so as to have the outlet distal or from the end of the piping, which may be ordinary gas-pipe, and the other three in bunches, so that the outlet is at nearly right angles, each about an inch below the other, and so placed thai they are one-third the circamfereuce of the main pipe apart, will be found, I thiuk, most serviceable in your groves. Such ;i bunob working from the center of an ordinary Bized tree will envelop it in a perfeol ball of mist. For tall trees a more forcible stream might be bad from theend l>y substituting an ordinary jel with a wire extension. This is a recenl device first brought to my attention bj Mr. a. II. Nixon, of Dayton, Ohio, and for Bending a fine spray for a great distance it has advan- tages. It is simply an extension screwed over an ordinary nipple, the end »>f the tube being covered with wire netting, which breaks up the liqnid forced through it. The brass nipple Bhould be about one inch in length, tin- perforation very true ami varj ing in diameter according to the tone of spray desired. 'I' in- nipple screws on the discharge pip"', ami upon a shoulder threaded for the purpose is screwed a chamber or tube about one inch in diameter ami three inches h'li-, to the outer end of which is soldered a piece "of wire gaUZC Varying in si/.e of mesh to suit the force of pump and the size of aperture in nipple. Finally, if a service of blind caps and Beveral sets of cyclone nozzle caps of varying aperture are kept on hand, the spra\ ing may lie ad- justed at wiil to condition of w ind, si/.c of tree, vX.c Your worthy president has very well remarked that what we want is not generalization, but hard facts ami experience presented iii the simplest and briefest manner. If I have dealt somewhat with princi- ples rather than with details, I shall look for your excuse in the fact that extended experience presents such a multiplicity of details as to warn me from entering into them. PUMIG \ ) [ON. Fumigating trees will always have, casteris paribus, some disadvantage ompared with spraying. The mechanism is more cumbersome ; the time required for treatment and the first cost in making preparation iter, ami these facts will always give Bpraying the advantage with small proprietors and t hose who are dealing with young trees. Sulphur fumes have been tried, but they burn the leaves and injure the tree. '1'obaceo smoke and vapor fail to kill the egg8. Ammonia IS excellent, but fails to kill all, though I have known the most beneficial results from the ammonia arising from sheep manure nsed as a fertilizer in apple orchards. I'd sulphide of carbon has been tried, and with great care in getting the right quantity its vapor will kill the insects without killing the tree ; but its application requires too much time and i> fraught with more or less risk to man. This is equally true of cyanide of potassium and of other substances the vapors from which are known to be very deadly to insect life. It will be difficult, therefore, to find ;i mode of fumigating that will be harmless to the tree and deadly to the disc and at the same time as rapidly ail e ksily applied as a spray. 22 Many of you already know that Mr. Coquillett, in connection with Mr. Alex. Craw and Mr. Wolfskill, of Los Angeles, have for some time been conducting a series of experiments which lead them to believe that they have discovered a gas which possesses the requisite qualities. The trees which I have examined that have been treated with this gas, both there, at San Gabriel, and at Orange, lead me to the conclusion that they are fully justified in this belief, and several ingenious contrivances have been perfected in Los Angeles County which give promise of great utility and feasibility. Whether the trees are left uninjured, it is per- haps premature to say. That they are affected is evident 1:1 some cases, and what the ultimate effect will be time alone will decide. Let us all hope that the promise of this gas will be abundantly fulfilled. Let me add, however, that even if it be found that no solitary insect or e^), after an examination of specimens <>t' /. saechari^ sent him by Signoret, says that he finds the " Mauritian species mi- donbtedly and markedly distinct." This letter to Mr. Klee brings up, however, the whole question of the accuracy of his determination. He admits that he has never seen Signoret's I. saechari alive. The only differeuces which he made in 1883 between 1. saechari and I. purehasi are as follows: "J. saechari does not seem to form an ovisac withlongi* tudinal grooves, nor does the body of the insect, although somewhat hairy, show the great tufts of black hairs and the curious projecting glassy tubes springing from large brown coroneted bases which are marked features of /. purehasi. The number of circular spinneret ori- floesare much smaller iu the .Mauritian insects.'* Now Signoret knew only two stages, the full-grown female and the newly hatched larva, while Maskell gave careful descriptions of the _. the young larva, the second stage, and the full-grown female, but had not seen the male larva, cocoon, or adult. It is for this reason that 1 have given a very full characterization of the species in the article already alluded to. Signoret's description. BO far as it goes, applies thoroughly well to /. purehasi in some ol its forms. His female had not formed the cottony or tinted-egg covering, at least he makes no reference to it. 1 1 is Bgure, while Showing a short truncated mass, does not indicate the (lutings because the few lines upon it are evidently intended by the attiM for 28 the long, fine, glassy hairs. Maskell, following Signoret's description, rightly says that sacchari "does not seem to form an ovisac with longi- tudinal grooves." But Siguoret himself says that sacchari, in the island of Bourbon, "is confounded with Leeanium (jasteralpha, under the name of louse- with -the- white-pocket." Whether Signoret assumed such confounding by the islanders because of erroneous supposition that this sacchari had no ovisac, or whether the islanders designate both the Leeanium and the Icerya under the characteristic vernacular, is not plain from the language, aud is immaterial. On the principle of unity of habit in the same genus, I feel morally sure that Signoret's Icerya must produce her eggs in such an ovisac, and the Bourbonese are doubt- less well aware of the fact, otherwise they would not so indicate it or confound it with Leeanium. "We are justified in assuming that the female which my friend Siguoret described and figured had only just begun forming its sac, and that its tlutings had become effaced and the secretion unnatural in appearance. Maskell's second reason, viz, thar sacchari "does not show the great tufts of black hairs aud the project- ing glassy tubes," will also lose force from the facts that Signoret par- ticularly describes these glassy tubes as " long filaments, waxy, very fine, delicate, transparent," and that these tufts of black hairs are ex- tremely variable in quantity, sometimes making the insect look quite dark and bringing out iu strong relief the few smooth, orange-red or brick-red elevations, and particularly the series of about twenty-two around the border ; at other times being so scarce that the insect has an almost uniform reddish-brown appearance. It would appear, therefore, that, notwithstanding the differences in Signoret's and Maskell's characterizations, there is room yet for grave doubt as to the specific difference in the two insects, especially as upon restudyiug Signoret's description it accords in every other particular with I. purehasi. You will pardon me, I know, for going into these technical details, be- cause it is evident that the solution of these questions has a very im- portant bearing. My own impression now is that future investigation will prove that the two insects are identical. The truth will in time be ascertained by getting all the different stages of sacchari from the Isl- and of Bourbon or from Mauritius, and comparing them more carefully with purehasi, the different stages of which I have fully detailed in my report. Let me say in this connection that there is a great variability in pur- ehasi as to the amount of matter secreted on the scale itself, which may very easily mislead, especially in dried specimens. In the orange proves of Southern California the general colorational aspect of the insect is, in all its stages, reddish-brown, the surface exudation being rarely ex- cessive and never obliterating the reddish-brown color. This exudation is, in fact, more noticeable upon the male larva, which, together with his narrower, more elongate form, renders him easily distinguishable 29 from the female, tn the more northern parte of the stair, however, 1 (band thai the general colorational aspeol was quite different, owing to the greater excess of the enrface exudation, which frequently covers tin- body in little globular masses and gives ii a whitish and even greenish aspect, and which often rises along the middle of the bod] into a tufted ridge. This form corresponds more nearly with whal Signorel has de scribed, and it follows thai this waxy Burface exudation becomes densei ami still more noticeable by contraction in the dried or cabinet speci mens or whenever the insecl has shrunken. This question of the synonymy of the Bpecies bears directly on its original source ; for if we have bul one species of the genus, or even if there be tWO, and /. piirclmsi is found to OOCUX on t lie BUgar cane in the islands of Bourbon and Mauritius, then the presumption will )>•• thai it originally came from these islands, in my address al Riverside, 1 called attention to the fact that this Fluted Scale seems to have heroine notably injurious almost simultaneously in Australia, South Africa, and California, and on the assumption that it infests the sugar cane on the islands mentioned, ii is much more easy to understand its introduction to the other eon n tries. Sugar is exported from those islands into in any parts of the world. The 80 gar, as ir leaves those islands, is very coarse, ami all the molasses or sirup is not extracted, centrifugals not being in use. For the purpose of draining, the Bugar-makers are in the habit of putting a piece of cane in every hogshead, and. in addition. 1 ii e top is sometimes covered with pieces of cane, in point of fact. I am in formed that an insect, known in the trade as the SUgar-louse, is Oi quite frequent occurrence in BUCh BUgar, and Professor Wiley, of the Depart- ment of Agriculture, upon being shown specimens of Tcerya purehani (and he is quite familiar with the so-called sugar-louse), informed me that he thinks them identical. On this hypothesis the initial spreading poinl is from someofthePacific islands, and the insecl probably made its way fust to Cape Town ami thence to Australia. New Zealand, and California. This does not pre- clude the possibility of its importation upon other plants, bul I think it highly probable that the chief method of distribution of an insect which is BO tOUgh as to bear long survival without food was upon BUgar- cane in sugar hogsheads, or bags, as it could be much more safely carried in this way than upon living plants. The determination of theoriginal Source Of the pest i* of vital concern in any study of its parasites, as such would be more apt to be found in its native country than in any countries of its introduction. I have been quite anxious to settle definitely this question of its oi - nal home, ami have lately hail Bomecorresp radence with parties in A.us tralia. New Zealand, and Africa. The following extracts from such correspondence will prove of interest to the people of California. Mr. Kirk's statement will add weight to the hypothesis that 1 have ventured, while Baron von Mueller's statement also strengthens it. It may per- 30 haps be impossible at this late day to definitely settle the question of this original source, especially as there may have been not one but several in- troductions (indeed we have evidence that such was the case) into all three of the countries iu which it now occurs; bat we can much easier understand its travels if it started as a sugarcane insect. I have itali- cized those parts of the following letters which particularly bear on the subject of this communication. The sketch of the Dipteron, which Mr. Crawford found attacking Icerya, shows a great likeness in the body to some hymenopterons En- cyrtids ; but the wings indicate its Dipterous character and that it be. longs to the Dolichopodidae near Diaphorus. So far as their larval habits are known, these dies are predaeeous and live in the larva state iu the ground. Perhaps Mr. Crawford has used the term "parasitic" synouymically with " predaeeous," but I will not further anticipate what Miss Ormerod may report.* EXTRACTS FROM CORRESPONDED 1 ,. [The following are the extracts from the correspondence to which ref- erence is made above. — Editors Press.] Letter from Roland Trimen, of Cape Town, to Professor Hiley. As regards the evidence as to the Australian habitat originally of this insect, I re- gret that I have, nothing to add to what has been already supplied to you. Since the commissioner's report in 1877, tbe orange industry of the western dis- tricts has suffered most severely, scarce, very interior, and exceedingly dear fruit be- iug now only obtainable where it used to be abundant, good, and (heap. Where, however, the kerosene and alkaline solutions have been constantly applied by indi- vidual proprietors here and there, the result (as I am informed by Mr. MacOwau, di- rector of the botanical gardens) has been very encouraging. In the eastern districts the effects of the Icerya's attacks do not seem to have been nearly so serious, but whether this is due to a less suitable climate and other conditions, or to more vigi- lance aud exertion ou the part of cultivators, I cannot at present determine. * Since this was written I have received two specimens of the insect itself through the courtesy of Miss Ormerod. These speenneus are so much in otilated that it is al- most impossible to accurately place them. The enlarged tigure 6eut by Mr. Craw- ford was very misleading, the venation of the wing being wrong and also the an- tenna'. It has no second cross vein ou the wings and no sort of resemblance to tbe actual antenna', while the two basal cells on the wings are lacking. It is quite likely that this fly belongs to a new genus. The specimens were sent to Dr. S. W. Willis- ton, who reports that he considers them Oscinids, but that further than that he could venture no opinion as he can locate them in no genus with certainty. In reference to natural enemies of the Icerya, it is of interest to note that a little lady-bird, Rodolia icerya, of which Miss Ormerod has sent me a figure, has been found to do good work ami to destroy the pest in Australia, while news comes from Cali- fornia that Chilocorus cadi is doing such excellent work that the trees in some local- ities are being entirely freed through its instrumentality and the lady-birds are act- ually being sold to orange-growers at so much per ounce. C. V. R. The bug spread to Natal within the last few | . • u i received in. us.. r them, (band on the oommoo block wattle rry to i lot found t li.-i i i be i ion in the in 1 1 1 .- r h is be< a i . My, In 1887, threw oat the attempted li on the md Tr! men, South African Museum, Cape Ton of Good Hope, Februan -. 186 F. & ( ear I entirely lost i ng to the b tracing of an unfinished drawing of tfa d. I know nothing about the Dlptera and should be obliged if yon oan determ the insect from the draw ing. I iu;i> s.iy ill. 1 1 [ sent Miss E. Ormerod specimens of the il\ abonl two months back, bnt, of oonrse, have not had time to hear what she makes of it. This is the onli instance I know , «>r ha ve re im always raised from seed, chiefly obtained from North Australia. It seems, therefore, more likely that when Acai as are grown anywh they would afford— particularly in humid climes— a favorable opportunity for the [cerya to spread. A similar circumstance occurred in Ceylon, and another in rome parts of Brazil, where an indigenous insect plague became aggravated, when Euca- lyptus, on which that insert preferably seized, became reared.* Whether the Icei was originally an inhabitant of Victoria or merely immigrated, I will endeavor to rtain; l>ut such a subject of inquiry is surrounded with difficulty now after half a eentnrj 's existence of the colony, particularly aa tln> [cerya drew no attention here by any extensively injorions in any cultivated plants, though it may have caused on some plants minor or transient injury. [ Ferdinand von Mueller, Melbourne, Australia. March 21, 1887. Letter from L. M. Kirk, of Wellington, New Zealand, I ir Biley. On returning from ., protracted tour of forest inspection in the South, I find your letter of2Sd December awaiting reply. My friend Baron von Mueller is mistaken in supposing that I have written recently on the Icerya purchaei. In a report on Fruit Blights printed two years ago, I drew attentioii to the pest, intending to treat at greater length at an early date ; but my do rvatoi have prevented the intention from being carried out. The insect it a native of the Fiji and other Pa* probably with orangi trees, to Australia, New Zealand} and < alifornia. Mr. \ ,v ivs t> .n - 32 I believe, that it is a native of Australia, and was introduced from that country on mimosa plants; but this is an error, and Acacias are rarely or never introduced as living plants, owing to their being so readily propagated from seed. The Icerya is abundant in the northern and middle parts of the Auckland district, and usually prefers eitraceous fruits; it is, however, found in large quantities upon some of the wattles, evincing a decided preference for the silver wattle (Acacia deal- bata). It is, however, occasionally found on furze, manuka (Leptoapermum scopari peach and apple, hut on these fruits only in small quantities, and not, so far as I am aware, doing serious damage ; in fact it is only found upon these plants when grow- ing in the neighborhood of infested Citrads. It is occasionally found on a few native trees, but it is not causing any great injury. It is also found in Napier and other parts of Hawke's hay, on the eastern coast of North Island, and in Kelson, and tin: northwestern corner of tin- South Islands. It is also said to he found iu Canterbury, but I have no direct evidence of its occurrence in tbat district. It is not found either in Taranaki or Wellington, in the North Island, except Nel- son and possibly Canterbury. There can be no question that it is a serious foe to eitraceous fruits and to wattles. In the vicinity of Auckland, and in many other parts of that district, it is abundant. I have seen trees greatly injured by its ravages, but cannot say that I have seen any killed. At present orange culture has not attained large dimensions here, but there can be no question that Icerya is the worst foe our orange-growers will have to en- counter. I have not seen an Acacia killed by this pest, although the under surfaces of branches are frequently covered. Iu a few established orange grounds the yield of fruit is ma- terially diminished by the ravages of this insect. No official documents have been published respecting the Icerya except the Fruit Blights report already mentioned, of which a copy of a Queensland reprint is inclosed herewith. The forest department has purchased Mr. Maskell's account of Scale In- sects and is about to publish the same with colored plates. A copy shall be forwarded as soon as it leaves the press. [L. M. Kirk, General Crown's Laud Office, Forest and Agricultural Branch, Wellington, New Zealand, March 25, 1887, From an article by E. J. Dunn, in Melbourne Argus, August 188 I desire to call attention to a species of Coccus known as Dorthesia. This destruc- tive pest uas first observed on the island of Bourbon. Thence it spread to Mauritius, about 25 years since. In Mauritius it destroyed the orange and lemon trie*, many of the orna- mental shrubs and Acacias, and wrecked most of the beautiful plantations and shrubberies. At Port Louis it still exists in loathsome masses on the handsome Talipot palms. About 12 years ago it was noticed for the first time in the Botanical Gardens, Cape Town, and most probably arrived there from Mauritius with plants sent to the Bo- tanical Gardens. During the first summer it spread about three miles into the sub- urbs along the railway. Its fearfully destructive character now became evident, for the orange trees, the Australian wattles, the pittosphorunis, and the blackwoods he- came loaded with this disgusting parasite, and the trees slowly but surely succumbed to its attacks. « » » . All trees of the orange kind, such as lemon, citron, shaddock, &c , proved especially suitable food for the Dorthesia, and once a tree became infested no amount of syring- ing or washing prevented its destruction. The disastrous results of its arrival at the Cape are all too evident. Formerly in Cape Town itself, and throughout the suburbs, the orange tree lent a charm to the gardens that no other tree could give, and in the Western Province orange-growing formed a most important sorrce of wealth, many farmers netting sev- eral hundreds a year from their orange groves. Some of these groves, planted by the Kogoenota and their descendants, were • md, besides being ] Itable, wen objects ..i great beauty, 'l bote of the Pe ni. Pn ooh Hot a and Wagenmal Vallej were especially famous. To-. lay tins is all ohanged, and, except for a fen dead stumps, these (ragranl groves and thia valuable asset in the country's wealth have disappeared. Not so theDortheaia; it la still advancing steadily, and leaving destrnetion In it* a she, ami will continue to il" so as long >- suitable food la « Ithin reach. in i Bull. Lfi 3 THE USE OF GASES AGAINST SCALE-INSECTS. [Beprinted from Bulletin No. 71, Agricultural Experiment Statiop, University of California. J Borne time ago the Agricultural I lepartmenl was requested by Messi s. A. I'». and A. s. Chapman, Mr. I.. II. Titus, and Mr. J. 0. Newton, prom- inent orange-growers of Los Angeles County, to conduct experiments with tlic \ iew of determining the efficacy <>t' certain gases as insecticides, with Bpecial reference to the White Scale. Icerya purehari. The follow- ing is a summary of results, of which a full report will he published hereafter : The use of gases for this purpose has been long contemplated, and various appliances have been BUggested for the ready application of any efficacious gas. The ease with which gas penetrates to all parts of the tree naturally BUggestS its use as preferable to washes, which at best leave many parts o\' the foliage and infested branches untouched, even When sprayed with the greatest care. In order that the gas may bean efficient insecticide it must be bo poisonous that even when applied in small quantities it produces fatal results; tor in the application the air confined in the tent covering the tree dilutes the gas to a great ex- tent. Again, the gas must be capable of bi ing generated quickly in sufficient volume. The record below .shows that only one of the ^ims employed fulfilled these conditions to a satisfactory extent. Prelimi- nary experiments with some others having shown their unfitness for the purpose, either on account of expense or because of injury to the foli- age, or imperfect action on the insects, their study was not pursued further. AlMM.l \N< is POB LPP1 [0 LTION. The tent for covering the tree is made of heavy bed-ticking, thor- oughly oiled with linseed oil. This cloth serves the purpose hot. as it is very closely woven, is pliable and easily folded. The support of the tent, devised by .Mr. Titus, is a very ingeniously contrived BCaflblding mounted on wheels, which seivc to move it from one tree to another. Its dimensions are 26 feet high, with a base 20 by I'd feet. Its upper part is 20 by 12, and carries upon the top a roller made Of galvanized iron (6 inches in diameter and 1_' feet long . upon which 36 the tent is rolled wheu taken from the tree. Side guy-ropes are at- tached to the bottom of the tent and run through pulleys at the upper corners of the scaffold. They are used to open the tent when it is to be dropped over the tree, and to fold it up when it is removed. The lightness of the apparatus allows of its being easily removed by two men, who operate the whole. If necessary, two or more tents can be handled by the same scaffolding, one tent being left over the tree while the scaffolding is moved to the next. In adjusting the tent, the bottom is placed on the ground about 3 feet from the tree and covered with earth. This brings the gas to bear upon the base of the tree and the surrounding soil. The Generator in which the gases were produced consists of a heavy sheet-iron cylinder, 11 inches in diameter and 13 inches high. The bottom rests on a plank, and to the top is fitted a movable cover sus- pended in a frame by a bench-screw. Into the cover are fitted two pieces of gas-pipe, one for the exit of the gas toward the tent and the other, connected with a pump, carries the gas which returns from the tent. Two small reservoirs are also inserted in the cover ; in these are contained the solutions which are to flow into the generator for the production of the gas. In order to establish circulati on and to force the gas into the tent, a pump is used which also serves to exhaust the gas from the upper part of the tent and to force it again through the generator. It is proposed to replace the pump by a small fan-blower, which is much more expe- ditious than the common pump which was used. THE G^SES EXPERIMENTED WITH. Among the gases used were chlorine, sulphureted hydrogen, am- monia, carbon bisulphide, carbon monoxide, carbonic acid, hydrocyanic acid, and carbolic acid vaporized by heat. Chlorine. — Some preliminary experiments were made in small vessels into which this gas had been introduced. Some infested branches were allowed to remain in them for times varying from five to thirty-five minutes without any noticeable effect being produced on the insect. Atmospheres more strongly saturated with the gas proved fatal to the insect in a short time. In other treatments extending over eighteen hours, with less saturated atmospheres, only a small percentage of the insects was killed. No decided effects were noticeable on the foliage unless the gas was very concentrated. • Carbon Bisulphide. — A lime tree, 12 feet in diameter of top, was treated with the vapor of 2i pounds of sulphide of carbon for forty-five min- utes. At the end of this time the insects were lively, and during the treatment had crawled up and collected around a rope surrounding the tree at the point where the gas was being injected from the hose. It proved that the gas thus used injures neither the insects nor the foliage. 37 ii is upon record, however, thai in oases where the vapor has not bees thoroughly diffused, bnl was allowed to Mow down from an open vessel placed in tin- top of the tent, serious injury was done t<» the foliage at points where the undulated vapor flowed down. Sulphureted Hydrogen. — Several treatments with this Mas were made on a small bo ale, the application lasting from five to thirty Ave minutes. The effects produced either with diluted or concentrated gas were simi- lar to those produced l>.\ chlorine, except that even the concentrated Bulphureted hydrogen did not injuriously affect the foliage. An ex- periment in which a whole tree was treated in the tent, for forty-flve minutes with quite concentrated siilpliuretcd hydrogen ,:;i\ showed clearly that the effect was tar from being satisfactory : the insects for the moment were Stupefied, but in the course ol'an hour and a half the majority of them were again moving about. Amnion in. — The vapor from one pound and a halfol Btrong ammonia water was applied to an Ll-foot lime tree f Or 30 minutes. The results were disastrous to the foliage : the leaves were all scalded, and in a \\'\v da\ sail dropped from the tree, and even the newer growth of wood was injured. The insects, however, were not perceptibly harmed. Carbon Monoxide. — Very strong hopes have been entertained by many tor the BUCOessful application of this gas. Its apparent cheapness and easy production, when the necessary plant is once erected, would tee Ommend it. Unfortunately our experiments show that it is not BUffl ciently effective to warrant its use. The gas was obtained by forcing air through a small furnace tilled with red hot charcoal, care being taken to cool and to measure the j,ms before applying if. No appreciable ef- fect was noticeable after 40 minutes. In a duplicate experiment, in which the charcoal was more Btrongly ignited and continuously intro- duced into the barrel for 30 minutes, only slightly better results were obtained. lie Arid. — It was thought that the production of carbon monoxide by decomposition of oxalic acid by heat might be substituted for tin- previous method of generating this gas. < )ne-quarter of a pound of ox- alic acid was ignited, and the gases applied in a manner similar to that of the preceding experiment. Neither the insects nor the foliage were harmed in the least. This experiment has incidentally shown that the vapor of formic and oxalic acids, also produced during the heating of the latter, is likewise ineffective Carbolic Acid. — It had been suggested that carbolic acid vaporized by heat would prove fatal to the insect. A dose of half a pound of liquid acid was volatilized in the furnace, and the vapor blown in the vessel Containing the infected branch. At the end of 20 minutes all tin- old insects were still alive, and some of the yonng ones, just molted. were moving about. An hour Liter the foliage appeared as if scalded. // droeyanie Acid. — It was only with hydrocyanic or prussic acid gen- crated by the action of sulphuric acid on potassium cyanide) that mu'Ii- 38 ciently fatal effects were secured to warrant a more thorough determina- tion of the time of exposure and quantities of material which would produce the best results. Numerous experiments were carried on for this purpose, and it was shown that even small amounts were effective. It was also shown that even in these small quantities an injurious effect upon the foliage was produced. In the beginning of the experiments, " mining cyanide " of potassium was used. It is a very impure material and contains along with the cyanide a considerable amount of carbonate of potassium. For this reason many of the first treatments were prac- tically ineffective. Later treatments with pure cyauide were more successful in destroy- ing the insects, but the foliage was proportionally injured. Treatments varying in dose from 4 to 12 ounces of cyanide, and in time from 15 to GO minutes, showed that the effect produced on the foliage by longer treatment was not proportionally greater thau that produced by short treatment. Neither was the effect of longer treatments proportionally more fatal to the insects. It was thus clearly shown that the gas mixt- ure should be of considerable streugth in order to insure rapid action. The effect of the gas was so disastrous to the fol iage that it became necessary to find some means of remedying this trouble. This was sought in applying a second gas, which might preserve the foliage. Sulphureted hydrogen was therefore injected into the tent, together with the cyanide gas, both from the same generator; a portion of the sulphureted hydrogen being introduced before the cyanide was gen- erated. It was found that the insects appeared stupefied when the tent was raised, but large numbers revived in a few hours. The effect of the cyanide seemed therefore to have been decreased by the sulphu- reted hydrogen. The foliage was net preserved, although not so badly affected as by treatments with cyauide alone. Carbonic acid gas was next tried. Trees were treated with larger doses of cyanide than heretofore used, and the carbonic acid from li pounds of carbonate of soda was at the same time introduced with these doses. The insects were killed and the foliage of a 12-foot tree re- mained unharmed, while that of a 14-foot tree with the same amount of carbonic acid was slightly injured. Thus it was shown that it would require l.J pounds of bicarbonate of soda to preserve tree tops 12 feet in diameter, and that with this protection the deadly cyauide could be successfully used. The regulation of the doses for the different sized trees so as to pro- duce uniform treatments is calculated on the basis of the results of the experiments which determined the amount of each constituent for a 12- foot tree. The following table indicates the amounts for trees of differ- ent dimensions of top, based upon the rates of cubical contents : 39 il tree, Cj»t l>. Ml Sulpl potassium ! 1 FhtU 1 , 7 . i S 1 I . II 8 7 • I i - 11 l i ■ i 10 ii. a 11 1 II 18 20 ii 11.8 II ■.''. t It 81.8 IS M 17 18 19 12 i I'D BU. 5 In onicr to apply the doses easily they are prepared so thai the re- quired amounts of each ingredient can be directly measured. The cyan- ide solution is prepared bydissolving, say, L0 pounds of the solid salt in about -1 gallons of water, wanned nearly to the boiling point, stirring at intervals, cooling, and then diluting to L'l gallons. This solution will contain about one ounee of cyanide of potassium to 2j fluid ounces of the liquid. The bicarbonate of soda is pulverized finely and measured off in a vessel marked, so as to designate pounds and fractions of a pound of the solid material. It is then placed in the generator, and the dose of Cyanide mixed with it, and, if necessary, a little water added to make it into a thin paste. After adding the measured dose of sulphuric acid, the pump is worked slowly at first, and moie rapidly alter the gas has passed into the tent. The time for each treatment must he determined by future experiments; fifteen minutes seemed to he quite Sufficient when the cyanide alone was used, hut it may he desirable to extend the treatment to thirty minutes when the foliage is protected by the car- bonic acid j, r as. It is advisable that the treatments should follow cultivation after about four days, so that all weeds anil places where the insert may find lodgment would be destroyed. The insect will then be mi, or very near, the tree: the fitting of the tent to the ground is thus also much easier. The eggs of the insect remained apparently uninjured wherever pro- tected by the woolly covering. A second treatment, to destroy BUCh as may afterward hatch, will, therefore, be necessary. It must not be understood that these experiments definitely settle the mode of Operation and the size of the doses to be used. They are inereh Buggestive of a general plan which can be so perfected in the future that the application of this remedy to other kinds of trees and insects must be attended with good results. 1 1 simply remains tor the Ingenious cul- tivator to devise the necessary appliances for its use. on ;i small scale, on all sorts of fruit trees, shrubs, and plants. 40 It must not be forgotten that extreme care in the handling both of this deadly gas and of tlie cyanide itself is necessary. To inhale the one or to taste or touch a wound \Wth the other may lead to serious con- sequences. F. W. MORSE. Berkeley, June 12. UNIVERSITY OF FLORIDA