University of California— College of Agriculture, AGRICULTURAL EXPERIMENT STATION. E. W. HILGARD, Director. PARIS GREEN FOR THE CODLING-MOTH. By C. W. Woodworth and Geo. E. Colby. Pure. Paris Green, as It Appears Under the Microscope. BULLETIN No. 126. SACRAMENTO: A. J. Johnston, : : Superintendent of State Printing. 1899. SUMMARY OF CONTENTS. With Page References. Paris green as now found on the market is often unsatisfactory (p. 3), occa- sionally a bogus article (p. 8), sometimes adulterated (p. 8), commonly low grade (p. 9), and very often with much free arsenic (p. 9), which is danger- ous to foliage (p. 9), especially in California (p. 10), and the injury from which cannot always be prevented by the addition of lime (p. 11). Pure Paris green will dissolve wholly in ammonia (p. 12) ; it will make a green streak on glass (p. 12), and consists of green spheres, as seen under the microscope (p. 13) ; the latter is the best test, but chemical analysis is neces- sary to determine the grade, and the presence of soluble white arsenic or arsenites (p. 14). Freedom from soluble arsenical compounds and a known grade are essential in a spraying material (p. 14). Laws have so far failed to recognize this (p. 15), and better standards are essential (p. 16). The Uni- versity of California will condemn all samples of Paris green that are not pure (as shown by the microscope), or if they contain water-soluble arsenical compounds, or if they fall below fifty per cent of arsenious oxid (p. 17). Under the present circumstances the use of substitutes for Paris green is recommended (p. 17). These can be obtained ready-made, in considerable variety, but there is no assurance that their quality will be maintained (p. 18). Home-made articles are the cheapest, are easily made, and have been quite thoroughly tested (p. 22), but they require more care in handling because of the danger of poisoning (p. 24). Other remedies for the codling-moth have been tried, and, under some circumstances, might be used to supplement spraying (p. 25), such as the use of bands (p. 25), destruction of "windfalls" (p. 26), destruction of moths in fruit-houses (p. 26), and traps (p. 27); while others, like winter spraying, are useless (p. 27). Mistakes, often made, which should be avoided are as fol- lows: Too few applications (p. 28), lack of uniformity (p. 28), and failure to appreciate difference of location (p. 29) and season (p. 30). The codling-moth can be fought effectively (p. 30) ; the correct practice is that which brings the best return for time and money invested in treatment (p. 31). This will vary with locality and season, and therefore requires intelligent considera- tion of conditions (p. 31) ; and finally the spraying must be thoroughly and carefully done (p. 32). Arsenious oxid soluble in water occurs in many samples of Paris green (p. 33); Paris green, if pure, though a variable compound, should be wholly insoluble (p. 34). The commercial article should not contain much over four per cent (p. 34). Objectionable samples showed on analysis from seven to thirty per cent of free oxid (p. 35). No really adulterated samples have been analyzed (p. 37). Some of the newer Paris green substitutes were examined (p. 37), including White arsenoid (p. 38), Pink arsenoid (p. 38), Green arsenoid (p. 38), and Paragrene (p. 39). The results are summarized on the last page. PARIS GREEN FOR THE CODLING-MOTH. By C. W. Woodworth. Paris green is practically the only substance that has been widely and extensively used as a remedy for the codling-moth. During the last three or four years a great deal of complaint has been made, both here and in the Eastern States, because of the failure to obtain the same good results as formerly, even by orchardists who do very careful work and have previously had the best of results. During this same period there has been a decided change in the microscopic appearance of most of the Paris green on the market, indicating a large amount of adul- teration on the one hand and a different and less satisfactory method of manufacture on the other. The situation became so thoroughly unendurable that this Station sent out the fol- lowing circular letter to the entomologists of the various experiment stations, and to the editors of a number of agricul- tural newspapers, in order to obtain the opinions of these parties and the facts in their possession: University of California, Agricultural Experiment Station. College of Agriculture, E. W. Hilgard, Director. Berkeley, Calif. Dear Sir : This Station has given considerable attention to the matter of the adulteration of Paris green, and we are convinced that at the present time there is scarcely any strictly pure Paris green on the market, whether here or in the Eastern States. It appears to me that it will be necessary for experiment stations and agricultural newspapers to cease to recommend Paris green as an insecticide the coming season, and substitute home-made arsenites. I write this note to request that you send me what information you may have upon arsenite of lime and arsenite of lead, especially as to their effect- iveness against codling-moth. This information I propose to compile and publish, giving due credit, and hope I shall secure your hearty cooperation. Yours truly, C. W. WOODWORTH. — 4 — Replies to this circular were received from the following persons, to whom acknowledgments are due: E. F. Adams, agricultural editor Weekly Chronicle, San Francisco, California; Prof. J. M. Aldrich, Moscow, Idaho; Prof. E. E. Bogue, Stillwater, Oklahoma; Prof. H. A. Bolley, Agricultural College, North Dakota; Prof. W. E. Britton, New Haven, Connecticut; Prof. Lawrence Brunner, Lincoln, Ne- braska; Prof. B. C. Buffum, Laramie, Wyoming; Prof. Geo. C. Butz, State College, Pennsylvania; Prof. Fred W. Card, Kingston, Rhode Island; E. P. Claebe, editor Press and Horti- culturist, Riverside, California; Prof. J. H. Comstock, Ithaca, New York; Prof. A. B. Cordley, Corvallis, Oregon; Prof. F. S. Earle, Auburn, Alabama; Director E. H. Forbush, Gypsy- Moth Committee, Maiden, Massachusetts; Prof. H. Garman, Lexington, Kentucky; Prof. C. P. Gillette, Fort Collins, Colo- rado; Prof. E. S. GofF, Madison, Wisconsin; Prof. H. A. Gos- sard, Lake City, Florida; Prof. H. H. Harrington, College Station, Texas; Prof. F. L. Harvey, Orono, Maine; Prof. U. P. Hedrick, Logan, Utah; Prof. Glen W. Herrick, Agricultural College, Mississippi; Editor Iowa Homestead, Des Moines, Iowa; Prof. W. G. Johnson, College Park, Maryland; Prof. K. C. Kedzie, Agricultural College, Michigan; Prof. U. H. Lowe, Geneva, New York; Prof. H. A. Morgan, Baton Rouge, Louisi- ana; A. N. Pearsall, editor American Horticulturist, Monroe, Michigan; Prof. A. L. Quaintance, Experiment Station, Georgia; Prof. P. H. Rolfs, Clemson College, South Carolina; B. N. Rowley, editor California Fruit-Grower, San Francisco, California; Prof. Geo. W. Shaw, Corvallis, Oregon ; Prof. M. V. Slingerland, Ithaca, New York; Hon. E. L. Smith. Hood River, Oregon; Prof. J. B. Smith, New Brunswick, New Jersey; H. P. Stabler, Yuba City, California; Prof. J. N. Stedman, Columbia, Missouri; Prof. Wm. C. Stubbs, New Orleans, Louisiana; Prof. H. E. Summers, Ames, Iowa; Prof. L. R. Taft, Agricultural College, Michigan; Prof. James Troop, Lafayette, Indiana; Prof. E. B. Voorhees, New Brunswick, New Jersey; Prof. Ernest Walker, Clemson College, South Carolina; Prof. F. N. Webster, Wooster, Ohio; H. N. Williamson, editor Oregon Agriculturalist and Rural Northwestern, Portland, Oregon. - 5 — Purity of Paris Green. There is by no means unanimity of opinion as to the char- acter of the Paris green usually found on the market, as can be seen by the following extracts of letters received: Professor Slingerland, of Cornell University, writes: "I can hardly agree with your first premises that there is scarcely any strictly pure Paris green on the market; at least, not in the State of New York, for here we have a law requiring Paris green and similar poisonous insecticides to contain at least fifty per cent of arsenic. Many samples of Paris green have been analyzed by our chemist here, and but very few of them are below this standard. We receive but very little complaint which would indicate that Paris green was impure." Again, from South Carolina Professor Rolfs writes: "I have used Paris green with good effect for a number of years, and have found it effect- ive this year." Professor Walker says: " It is probably less (adulterated) now than formerly," and cites considerable number of analyses made by that station showing the total arsenic to be above fifty-five per cent. Professor Harrington, of the University of Texas, writes: a This is the first year we have had a law in this State controlling the sale of Paris green and poisonous insecticides. We have analyzed a number of sam- ples this year and found most of them pure. They were mostly from New York manufacturers." Professor Garman, of Ken- tucky, writes: "The samples of Paris green analyzed here, in some cases proved to be imitations, but most of those we have used contained fifty per cent and upward of arsenic — evidence that they had not been tampered with. However, I have not given special attention to the adulteration of insecticides, and it may prove that Paris green commonly sold from groceries and drug stores is more often adulterated than our experience would indicate. The Paris green used by me has been obtained mostly from well-known and reliable dealers in insecticides." Professor Taft, of Michigan Agricultural College, writes: "My experience with Paris green has not resembled yours, so far as finding it adulterated is concerned." Professor Gillette, of Colorado, writes: "The few tests that we have made here of Paris green indicate that this poison is fairly pure." Finally, Professor Cordley, of Corvallis, Or., says: "Last year our chemist, Professor Shaw, made something of a study of the 2ub — 6 — Paris green sold in the State, and reported it as reasonably pure." Professor Smith, of the New Jersey station, writes: "We have not found any willful adulterations. We have found very great variation in arsenic contents." The evidence on the other hand, showing the adulteration of Paris green, seems quite as extensive. Professor Johnson, of Maryland, writes: "Have had much trouble with l bogus' Paris green." Professor Quaintance, of Georgia, writes: "I heartily agree with you in your sentiments concerning this article, and am convinced that Paris green is being greatly adulterated. This seems particularly probable from the uncertain results which, from my own experience, I have had to follow from the use of this arsenite." Professor Troop, of Indiana, says: "I have been of the opinion for some time ihat the Paris green on our markets was not the pure article, because of the numerous letters that I have received complaining that it did not do the work." Professor Webster, of Ohio, says: "I certainly believe that what you say is correct, for I can seldom get the same results where it is recommended for a particular purpose to a considerable number of corre- spondents. Frequently, I find that in the hands of one per- son the Paris green is effective, while another one using it equally carefully, has failed entirely. Of course, I have but one way of accounting for this difficulty." Mr. Pearsall, of Monroe, Mich., writes: "There is no doubt that the adultera- tion of Paris green has grown to such an extent that in many cases the effects of its use are practically nil, and some substi- tute must be found." Professor Steadman, of the University of Missouri, writes: "It is very difficult for horticulturists and farmers of this State to get really pure Paris green, or London purple; almost impossible if they procure it at their little country towns. I have seen samples of Paris green that con- tained no poison of any kind. It was plaster of paris colored with indigo and chrome yellow." Professor Brunner, of Nebraska, remarks: rt We have also had considerable trouble of recent years in finding our experiments to be very uncertain and irregular. Our correspondents have, also, from time to time said that the results obtained by using this poison for the destruction of insects have been uncertain. They also ascribe the difficulty to impure poison." — 7 — In California the opinions of fruit-growers are almost unani mous in regard to the unreliability of Paris green, as they obtain the best results at times, and at other times very poor. A few quotations will be sufficient to indicate this: E. P. Claebe, of Riverside, writes: "I referred the circular to the president of our Horticultural Club, who reports that the experience of horticulturists regarding Paris green has been very unsatisfactory." H. P. Stabler, of Yuba City, writes: "We are ready to agree with you that the goods are generally adulterated." B. N. Rowley, of San Francisco, writes: "I have been aware for some considerable time that growers were spending money and wasting their time spraying trees with what they thought was Paris green, in which there was not enough poison in a gallon to kill a single codling-moth, but so long as the people want things cheap and keep crowd- ing down the price, manufacturers are bound to supply the demand, and adulterations follow. If fruit-growers are willing to pay the price they could be supplied with pure Paris green, or as nearly pure as factories can produce it. This would compel buyers in small quantities to pay possibly twenty- seven or thirty cents a pound. They prefer to buy chalk and salt and various other substances at ten and twelve cents a pound, wasting both time and money." These differences of opinion are explainable in a number of ways: they may be due, in part, to the fact that in some cases the samples of Paris green obtained and analyzed by station workers were from firms of known integrity; in part, to the fact that in some cases they were obtained after laws had been enacted requiring a certain standard of excellence; and in a measure, also, because this standard (the presence of fifty per cent of arsenic) is one very easily obtained, even in badly adulterated samples, providing part of the adulterant be arsenious oxid. On the other hand it is undoubtedly true that complaint is often made of the quality of the poison, when the whole fault lies with the user. A considerable number of samples made and sold in New York under the names of leading makers have been recently examined and condemned by us, mostly on microscopic evi- dence, though subsequently confirmed chemically. They prove that the situation in the Eastern States is no better than in — 8 — California. A large jobber writes that none better can be found on the market than these condemned samples. It is not contended that there is wholesale willful adulteration of Paris green, nor that a large proportion of the material sold will not come up to the legal requirement of the States which attempt to control its purity. The fact is nevertheless easily- demonstrated that but little of the Paris green on the market is really a satisfactory article for spraying purposes. Forms of Impurities. Three distinct classes of unsatisfactory Paris green can be recognized, which we would designate, respectively, as bogus, adulterated, and low-grade Paris green. Bogus Paris Green. — Under this title is included that series of out-and-out imitations of Paris green in which the color is produced from other substances than copper, and which usually contain no trace either of copper or of arsenic. They are usually perfectly harmless to the plant and to the insect, and quite decidedly cheaper than Paris green. They are sold mostly by paint dealers, and were probably manufactured for use as a cheaper form of green pigment than is Paris green. We have very little information of their extensive sale in California as Paris green, though both Mr. Rowley, of the " Fruit Grower," and Secretary B. M. Lelong, of the State Board of Horticulture, have met with samples sold as bona fide Paris green. It is probable that none of these articles would stand the ammonia test described below ; certainly, they would be at once recognized under the microscope. Adulterated Paris Green. — This class of Paris green is often sold by unscrupulous dealers — sometimes by honest dealers who have been supplied by unscrupulous jobbers — and indicates always an intention of fraud on the part of some one. They consist of Paris green in part, generally upward of fifty per cent, and to this is added some other substance for the purpose of increasing the weight. Any white powder, such as gypsum, will do, and even flour has been used. The intensity of the green color in good Paris green allows considerable addition of white material, though in some cases green or blue pigments are added to prevent detection. Most of these forms — 9 — of cheapening Paris green are at once recognized in all three of the tests given below, and especially are they at once detected under the microscope. Low-Grade Paris Green. — The third type of unsatisfactory Paris green, and the one most difficult to recognize, is a "low- grade Paris green"; by which term it is intended to designate those manufactured in such a way as to contain a low per cent of arsenious oxid in combination. A strictly pure Paris green can be produced, according to our observations, with not over forty per cent of arsenious oxid, but such a sample is simply low-grade. To use such in spraying would require nearly one- half more material to produce effective spraying, than would be necessary with a sample containing the normal fifty-eight per cent of arsenious oxid. For this class of green it appears that the only test now available is the chemical determination of the quantity of arsenic present. The production of low-grade Paris green is almost as expen- sive, or perhaps quite as expensive, so far as the ingredients used are concerned, as is the production of the high-grade article. It therefore appears that the low-grade greens are produced not with any intention of defrauding the public, but rather because of the ease of manufacture. The laws, especially of New York where the greatest amount of Paris green is manu- factured, require the total arsenious oxid to be above fifty per cent, and this has required the addition, either during or after manufacture, of sufficient arsenious oxid in the free state to come within the requirements of the law. As a result of this the greater part of the low-grade Paris green on the market contains as an adulterant a considerable proportion of the free acid. The determinations that have been heretofore made have only taken into consideration the total arsenic per cent, and so all these samples of low-grade, "doctored" Paris green have been passed as pure. Danger from Arsenical Adulterations. White arsenic (arsenious oxid), as has long been known, is very injurious to foliage; for this reason, it is scarcely at all used for the destruction of insects. It is much cheaper than Paris green, and were it not for the injury to foliage would — 10 — have been used entirely instead of Paris green. The one thing which has made the latter the standard insecticide has been its insolubility. Of late years, since the addition of free white arsenic has become a common practice by the manufacturers, or by adulterators, the unreliability of Paris green in its influ- ence on foliage has been repeatedly noticed. In the hands of the farmer this is almost sure to result in a diminution of the dose until the injury becomes unimportant. On the farm it is the practice to weigh and measure things very carelessly, and the difference between full measure and scant measure, even when the farmer thinks he is following directions, amounts to a very great deal. The diminution of dose has been one of the causes, and an important one, of the complaint of the inef- fectiveness of Paris green, which we have heard from all over the United States, during the last few years. The danger to foliage from free arsenic has also resulted in the change of the formula now usually recommended, by attempting to neutralize the soluble substances in the Paris green by the addition of lime. This matter will be referred to again below and in more detail. The addition of lime has been more or less successful when the amount of arsenic was not too large, but one of the great advantages of Paris green — that which more than anything else has caused it to hold its own as an insecticide — is the fact that no preparation is necessary. The substance as it is purchased from the store is stirred up in water and is at once ready for use. If it is necessary to add some material to neutralize the free arsenious oxid, it will be better to take slightly more trouble and decrease the cost of the material by the use of home-made arsenites. Causes of Injury to Foliage. While Paris green is entirely insoluble in pure water, it appears that as ordinarily used a certain amount of it does find its way into solution and thus enters the plant; and if very much goes in, the death of the part of the plant thus poisoned ensues. The most critical period seems to be the time during which the spray remains wet upon the leaf, and each subsequent wetting of the leaf from any cause, such as a fog or dew, continues the danger. It has been demonstrated repeatedly that dry Paris green can be placed upon a leaf in — 11 — any quantity, and so long as the leaf remains dry no evil results will follow. After an application in the wet way, almost immediately, within twenty-four hours, a blackening of the leaf or of parts of the leaf may occur, or the leaf may entirely escape at that time, but later, after a dew or fog, show the signs of the action of the poison; or again, there may be no blackening of the leaf observed at any time, but the leaf may become prematurely yellow and drop off within two or three weeks from the time the application was made; showing that the poison which entered the plant, though not enough to kill it at once, deranged its functions to such an extent as to cause this premature dropping. These two forms of poisoning we have designated as the acute and the chronic poisoning of arsenic. The amount of poisoning that may occur, other things being equal, seems to be entirely dependent upon the amount of soluble arsenic in the spraying mixture, though there are con- ditions of the plant when it is possible to spray even with a solution of arsenic and produce no evil effects. We know that under certain conditions leaves will absorb water, and under other conditions not at all; so it may be supposed in cases where solutions of arsenic have been applied without injury, that the plant was in such a condition that no absorp- tion of water took place and none of the arsenic solution entered the plant; and that before the leaves became again absorbent the water had evaporated, leaving the arsenic upon the leaves in a dry form. This might flake off and blow away from the leaves before they are exposed to a dew or fog. It may be that when we know more about the effect of weather upon the leaves, we will be able to spray at times when the leaf is least susceptible to injury, and so lessen the danger to the plant. Prevention of Injury. — A chemical means of avoiding the injury of Paris green has been used considerably. It con- sists in adding a large amount of lime to the water in which the Paris green is mixed, and this appears to be sufficient to render insoluble any slight amount of free arsenic or other sol- uble arsenites that may be present. The use of lime with Paris green has now come to be recognized as a very important pre- cautionary measure in preparing this spraying material, chiefly because of the presence of white arsenic in the Paris green that — 12 — has been manufactured of late years. The amount commonly recommended varies from one to ten parts of lime to each part of Paris green. If the amount of free arsenic in the sample is not too high, good effects will result from adding the lime; but beyond a certain point the lime does no good and may even do harm. It has long been known that lime acts on white arsenic, when the latter is in suspension in water, in such a way as to render it much more injurious to foliage than the arsenic would have been without the lime. Tests for Purity. There are no simple tests which will enable a person to quickly determine absolutely the purity of any given sample of Paris green. A great many forms of adulterants, however, can be immediately detected. Samples showing any consider- able variation in color, especially an abnormally pale shade, is an almost certain indication of adulteration, and those showing a tendency to dampness, or caking, should be rejected. Two or three methods are available for recognizing most of the more conspicuous impurities. Ammonia Test. — Paris green dissolves freely and wholly in ammonia, becoming a beautiful blue liquid; while a majority of the substances formerly used in adulterating a green are insol- uble. This, therefore, is a very ready means of recognizing most of the crude forms of adulteration. If upon treatment with ammonia any of the material fails to dissolve, the sample is adulterated. This test, however, is not conclusive, since white arsenic and a number of other substances used in adul- terating Paris green, especially in these later years, are soluble in ammonia and would escape detection if this method alone were depended on. Ammonia then affords valid grounds for rejecting a sample if any portion of it is insoluble ; but other means must be used to be sure of its purity, even if apparently pure by this test. Glass Test. — A very simple test, which will enable one to distinguish quite a good proportion of adulterated samples at once, including many of those not detectable with ammonia, is to take a very small portion of Paris green — what one could easily pick up on the point of a penknife — place this upon a — 13 — piece of glass, holding the glass at an angle; jarring the lower edge will cause the little pile of green to move down the inclined surface, leaving behind it a bright green track, if the sample is pure ; but in the case of many adulterated or impure samples the track would be white, or pale green. The method of doing this is clearly shown in the accompanying plate. The glass test is particularly useful in comparing a number of samples, and after one has acquired some experience it becomes quite reliable. It does not enable one to detect the recent forms of arsenic adulterations, and like the ammonia test, should never be considered as conclusive evidence of purity. Microscopic Examination. — By far the most satisfactory of all the easy methods for the testing of Paris green is the use of the microscope. For this purpose the sample is placed on a slip of glass and treated in the way just described for the glass test ; the glass slip is then put under the microscope and examined with a medium power objective, about one-quarter inch. The Paris green will be seen in the form of clean, round balls, and in a perfectly pure sample these are all that can be seen. In impure samples there will be observed, in addition to these green spheres, a considerable quantity of material of crystalline or irregular shape, usually of white color, the pure green being quite as distinct from the adulterants as seen 3tjb — 14 — under the microscope, and as easily recognized as wheat can be distinguished from the dirt that might be mixed with it. There is more difficulty in distinguishing Paris green con- taining an excess of free arsenic. This sometimes is added in the form of a powder, and is then as easily recognized as any other form of adulterant ; but when added in the process of manufacture it is firmly attached to the particles of Paris green, and only produces the effect of making them somewhat irregular, and causing a tendency toward sticking together. A study of the figure on the title-page will enable one to distinguish the pure green from the adulterated sample. The size of the particles of Paris green may be larger or smaller, according to the method of manufacture ; and the grade of the material may vary greatly and can only be properly deter- mined by chemical tests. Requirements for Spraying Purposes. Paris green was originally wholly, and is still in part, manu- factured for use as a pigment; but the requirements for this material when used as a spray are somewhat different from what is necessary for a paint. For paint purposes, one of the prime requisites is color; next to that perhaps, insolubility in water, upon which depends much of the wearing quality of the paint. For spray purposes the color amounts to nothing; insolubility is an essential, because upon this depends the safety of the plant; and in addition to this there must be suffi- cient poison (white arsenic in combination) to be effective as an insecticide. It has been known from the first that Paris green is not a definite chemical compound, but may vary considerably in its chemical constituents. It has, however, a definite physical structure and characteristics. As stated above, a good sample of Paris green consists almost exclusively of clean, round, green crystalline masses of uniform size and appearance, and with scarcely a trace of any foreign matter. While it may not be possible to make a Paris green which is absolutely pure (that is, which consists entirely of these green spheres), the older methods of manufacture produced an article approaching very closely to this ideal. The Paris green now in the market contains generally a very appreciable per cent of material not — 15 — combined in a way to show these characteristic crystalline masses, even when the chemical composition approaches very closely to the theoretical proportions. One of the greatest faults of the methods of manufacture now mostly used, viewed from the standpoint of the farmer, is the diminution in the amount of arsenic in combination. An analysis given in the latter part of this Bulletin, of a sample of Paris green showing fair color and which would possibly be considered a fairly satisfactory paint pigment, contains about one half the amount of arsenious oxid that has been supposed to be present in pure Paris green, and in addition, in an uncombined form, nearly one quarter of its weight of free white arsenic. It is possible that in this particular case, the free white arsenic may have been added because the laws of New York require the total arsenic to be at least fifty per cent. Such a sample would be very unsafe to apply to the foliage of plants, and especially so under the climatic conditions existing in California, as is shown elsewhere. There does not seem to be any evidence that the larger manufacturers of Paris green have intended to place upon the market anything other than an acceptable article. The sample of Paris green referred to certainly cost the manufacturer fully as much as one conforming to the usual standards. Apparently he found that his Paris green failed to meet the requirements of the law. and not having knowledge of the danger of white arsenic to foliage, he added a sufficiency to meet these requirements. Laws Concerning Paris Green. A number of the States, including New York, Louisiana, Texas, and Oregon, have enacted laws requiring the Paris green sold on the market in those States to contain fifty per cent of arsenious oxid. These laws differ somewhat in detail in the different States, but agree in establishing this standard for purity. Apparently, the only requirements of the laws in any of these States is that the substance sold as Paris green shall contain at least this minimum amount of arsenious oxid. Since arsenic is the cheaper ingredient in Paris green, it is evident that this law could be taken advantage of by the manufacturers or dealers and an inferior article placed on the market, containing any combination of material so long as it — 16 — is green and contains sufficient of this comparatively cheap substance. There is nothing in the laws, nor has there been any attempt by the chemists in charge of the analyses made under the laws, to distinguish the amount of uncombined, or soluble, arsenious oxid in the substances sold as Paris green. Such laws may be satisfactory to manufacturers or dealers, but certainly leave very much to be desired from the standpoint of fruit-growers or agriculturists in whose benefit they are supposed to have been enacted; they show evidence of the fail- ure to appreciate the real situation by those who frame the laws. In most of these States the laws are well provided with means to secure their enforcement, so that by remedying the defect pointed out above, by the establishment of a truer standard of purity, the markets would again be filled with a satisfactory Paris green. Manufacturers are not so blind to their own interests as to fail to meet any clearly defined demand. They stand anxious and ready to meet any reasonable require- ment the fruit-grower may make. Standards of Purity and Quality. It is evident from what has been said in the above discussion, that the chemical analysis which simply shows the total per cent of arsenious oxid is not a sufficient criterion either for purity or quality in Paris green. Arsenic is certainly the active principle, and everything else being equal the effective- ness of the insecticide is directly proportional to the quantity of arsenic present. The different arsenical compounds have each a somewhat different degree of efficiency, and the poison- ous effects differ more or less also with each insect and plant. The difference in efficiency of the various compounds is in a good measure dependent upon the chemical and physical con- dition of the arsenic in the various combinations. For instance, the killing qualities of Paris green and arsenate of lead, when used against the gypsy-moth, even when the amounts of arsenic present in the two applications are equal, are quite appre- ciably different. It will be necessary, therefore, that the exact condition of the arsenic in a spraying compound be specified and determined. The presence of free arsenious oxid, or of arsenic in any soluble form, should be determined in every case, — 17 — because it is a particularly dangerous impurity. In the case of such substances as Paris green which have no definite chemical formula the character of the material can be best determined by microscopic examination, confirmed always, of course, by a chemical test. To pass as satisfactory, the microscope should show the proper crystalline forms as composing practically all of the substance. In addition to this there should be an entire absence of all free arsenious oxid, and the Paris green should be of sufficiently high grade; that is, one containing a sufficiently large amount of arsenious oxid in combination. Exactly what this grade should be is a matter which deserves some consideration. When a Paris green can be made containing nearly sixty per cent of combined arsenious oxid, and another containing not over forty per cent, it is evident that very different results will be obtained by the use of the two forms, as it would take three pounds of forty per cent green to equal the effectiveness of two pounds of sixty per cent. The laws in the Eastern States have uniformly adopted fifty per cent as the standard, and possibly it would be well to retain this as the standard, though it would seem better, in order to secure greater uniformity, to make the standard fifty-five per cent; or to treat Paris green in the same way that fertilizers are treated, viz: have the percentage certified to and stated on the samples, so that forty, fifty, fifty-five, or sixty per cent might be sold on the market, each grade under its proper label. This is a matter, however, that w T ill have to be decided after a more careful consultation between the interests involved. For the present, the standard which this Department will require in samples of Paris green is : First — The sample will be expected to contain, as seen under the microscope, only a trace of foreign matter; Second — That the total of arsenious oxid shall exceed fifty per cent; Third — That the samples shall contain practically no free arsenic or other soluble arsenical compounds. Substitutes for Paris Green. A good sample of Paris green is a satisfactory article for killing codling-moth, and it has been tested so long under all sorts of conditions, and proven itself thoroughly satisfactory; and, moreover, as it can be had everywhere and requires no — 18 — preparation, it is altogether an extremely satisfactory remedy to use. The unreliability of the substance, however, is such that unless one is assured of the quality of the sample he intends to use, the only safe procedure is to use one of the substitutes hereinafter described. Not only the unreliability but also the cost of Paris green has caused many to look for a substitute. This search has been sufficiently successful to in- cline many to the opinion that Paris green never can again take the almost exclusive place it formerly held among this class of insecticides. A number of compounds have been suggested and more or less thoroughly tried for this purpose, and the results obtained in some cases have been very highly satisfac- tory. There are quite a number of substances of this character already on the market, and some can be very easily and cheaply manufactured at home. READY-MADE COMPOUNDS. The convenience of being able to apply an insecticide without any preliminary preparation will always favor a ready-made as compared to a home-made article. Very few of those now on the market have been sufficiently tested for the codling-moth to enable us to recommend them, but they might be well worthy of trial in a small way by the orchardist. It should be under- stood, however, that at the present time we have no assurance that these ready-made substances are uniform or will remain uniform in composition and efficiency. As with Paris green, a standard of excellence should be established and maintained by law. COPPER COMPOUNDS. The simple arsenite of copper usually known as Scheele's green has been used and recommended quite highly as a sub- stitute for Paris green. When pure it has a definite composi- tion and crystallizes into smaller crystals, and in both of these respects being distinctly better than Paris green. There seems no reason why it might not be entirely satisfactory for codling- moth work, though I have no data in regard to its effectiveness for this purpose. Other forms of this compound have been sold under the names of Paragrene, Green arsenite, Green arsenoid, and Laurel green. Of the first two I have favorable reports from — 19 — Maine and New York. Green arsenoid has proven in our hands rather injurious to foliage, and Laurel green did not prove satisfactory in the hands of Professor Harvey of Maine. Some of these are very far from being pure arsenite of copper. BARIUM COMPOUNDS. Barium arsenite is not uncommonly used as an adulterant in Paris green. Under the name "white arsenoid" it is sold for spraying purposes. Samples examined by us were very unsatisfactory, being very soluble and injurious to foliage. There seems to be no reason why it might not be all right if it is practicable to make it insoluble. LIME COMPOUNDS. London purple is the oldest of the Paris green substitutes on the market. It is an arsenite of lime produced as a by- product in the manufacture of aniline dyes, and contains cer- tain organic material which gives to it the purple color. It has been quite extensively used for codling-moth, and has gen- erally been considered an exact equivalent of Paris green in its effectiveness. It often contains considerable free white arsenic, sometimes to such an extent as to make it excessively injurious to foliage, and for this reason, more than for any other, it has nearly dropped out of use in a large part of the country. It has a definite advantage over Paris green in its lighter weight and finer grain, which enables it to remain in suspension in the water very much better, and therefore more likely to be evenly distributed. Were it not for the danger to the foliage, London purple could be highly recommended for codling-moth work. Arsenite of Lime. — The simple arsenite of lime seems to be the only substance besides London purple that has been exten- sively tried for codling-moth. Professor Lowe, of New York, writes: "Some of the leading growers in this vicinity used the arsenite of lime last season with excellent results. " Professor Slingerland says: "I have reports from some of our best fruit- growers that they have found the arsenite of lime even more effectual than Paris green, and, of course, a great deal cheaper." In Michigan, where the arsenite of lime has been more — 20 — extensively used than elsewhere, it seems to have been very satisfactory. Professor Taft writes: "I began nearly five years ago to recommend the use of arsenic, owing to its superior cheapness. As a rule, the price of arsenic as compared with that of Paris green has rendered it about one sixth as expen- sive, and, although I would not go so far as you do regarding impurities in Paris green, I am sure that the danger of finding adulterations in arsenic will be much less. I first began the use of arsenic in an extensive way upon the college orchards (nearly fifty acres) in 1895, and have used it ever since, buy- ing it at the rate of a hundred pounds at a time and employing it also upon potatoes and all other crops upon which I formerly used Paris green. While arsenite of lead proved effective and less likely to injure the foliage than Paris green, when the latter was used in water without lime, its cost made it, in our minds, far less desirable than arsenite of lime, or even Paris green when the latter was used with lime." Professor Brunner, of Nebraska, writes: "We have not thus far had much experience with the arsenites of lime or lead, but seem to have better results with the former than with Paris green." In Oregon arsenite of lime seems to have been extensively used of late. Professor Cordley writes: "We have given but little attention to the various substitutes for Paris green. On a small scale, however, we have tested both the arsenite of lime and the arsenite of soda (Kedzie's) mixture, and have found them satisfactory. Owing to the high price of Paris green many of our Hood River apple-growers have used the arsenite of soda for the past two years, and have yet to hear any complaint regarding it. Mr. Williamson, of Portland, writes: "I would say that a considerable number of fruit- growers in Oregon and Washington have used arsenite of lime as a substitute for Paris green, and in every case, so far as I have heard, with satisfactory results. It has been found to be fully as effective as good Paris green and much cheaper." Hon. E. L. Smith, of Hood River, writes: "I saved ninety-five per cent of apples free from codling-moth, and one of my neigh- bors did even better than that." Professor Hedrick, of Utah, writes: "We have used arsenite of lime at this station for two seasons with marked success." — 21 — It will thus appear that arsenite of lime has been quite thoroughly tested and with the best of results. In most cases the home-made article was used. A number of dealers have arsenite of lime on the market, and if one could be assured of its quality there seems to be no reason why they should not replace Paris green, on the score of cheapness. LEAD COMPOUNDS. Arsenite and Arsenate of Lead. — These compounds are used in Massachusetts by the Gipsy-Moth Commission as a substitute for Paris green, as the latter appears to be particularly ineffec- tive when used for the gipsy-moth larva. Arsenate of lead is distinctly better for these larvse than the arsenite, though both substances Have been extensive^ experimented with in all of the New England and Middle States. Professor Britton, of Connecticut, writes: "Have prepared and used arsenate of lead with good results. I cannot testify as to its effective- ness against the codling-moth, but expect it to prove satis- factory against any eating insect where Paris green is commonly used." Professor Slingerland writes: "The arsenate of lead is being quite extensively used in Albany and possibly in some other places in Hudson River valley for the elm-leaf beetle. I do not know that any one has used the arsenate of lead in this State for the codling-moth." Professor Smith, of New Jersey, has for years recommended the use of arsenate of lead, but gives no data regarding its effectiveness for the codling-moth; like- wise, Professor Butz, of Pennsylvania, notes that it is an effectual substitute for Paris green, but has not used it on apples for the codling-moth. The same is true of Professor Quaintance, of Georgia. Professor Garman, of Kentucky, writes: "I have used arsenate of lead and consider it a useful addition to our insecticides, because of the ease with which it can be kept in suspension; also because it can be used very strong without injury to foliage. Some insects, such as grasshoppers and blister-beetles, are not easily killed with the ordinary mixtures of Paris green. The arsenate of lead is a convenient substitute for such cases when it can be used without danger to man." Similar reports come from Professor Webster, of Ohio, who used it against the fldia of the grapevine. Professor Stedman, of Missouri, writes as to arsenate of lead and arsenite of lime: " I — 22 — have found no difficulty whatever in using them wherever Paris green will prove valuable. So far as I can see they can be used as a perfect substitute." HOME-MADE COMPOUNDS. The cheapest arsenical compounds are certainly home-made mixtures. The method of manufacture of these substances is very simple, and there seems to be no reason why they might not be used almost exclusively. Arsenate of Lead has not been tried for the codling-moth, as reports received in answer to our circular show, but the highly satisfactory results obtained upon other insects and the per- fect safety to foliage would indicate that it might be extremely profitable to experiment with. There are two methods of making arsenate of lead, which produce substances somewhat different in chemical structure, but about equally effective. In each method sixty-eight per cent of arsenate of soda is used, and with this, in one case, the ordinary white granular acetate of lead, and in the other, lead nitrate. The process of manu- facture is as follows : The lead salt and arsenate of soda are dissolved separately, and then poured into the tank containing the water for spraying. The proportions used are about as follows : For every ten ounces of arsenate of soda take twenty- four ounces of lead acetate or twenty ounces of lead nitrate. These substances can be purchased in the right proportions and tied up in bags, so that it will take one bagful of each for each tank of water. The amounts given above are sufficient to make about a pound of the pure arsenate of lead, which would probably be enough for one hundred and fifty or two hundred gallons of water. It can be used with perfect safety several times as strong as this. As a precautionary matter, it might be well to test the mixture in order to be sure that the arsenic is all in combination, which can be done by the use of potassium bi-chromate, which will produce a yellow precipitate if the solution contains lead in excess, as it should. Arsenic and Lime. — Very satisfactory directions for making this mixture are given in a letter from Professor Taft, of Michi- gan, one of the first who extensively experimented with it; ERRATUM. In line 1(5 (above) omit of; reference being made to the common, com- fi«% ffrade of arsenate of soda. VTlOWO'l — 23 — he writes : "I have had excellent results from boiling one pound of [white] arsenic and two pounds of lime in two gallons of water for forty minutes and then diluting as required. When one pound of the arsenic prepared as above, is used in every three hundred to four hundred gallons of water, I have found it equal to Paris green for destroying codling-moth and curculio, while one pound answers for one hundred and fifty to two hundred gallons of water when it is used upon potatoes; unless used in Bordeaux mixture, I find it best to add a small amount of lime when diluting. As the wholesale price of arsenic has averaged about seven cents per pound for a number of years, while Paris green has wholesaled at eighteen cents, it is evident that the latter is fully five times as expensive." In reference to the comparative value of arsenic with soda and lime, he further writes : "While some recommend the use of sal-soda to dissolve the arsenic, we have not found it neces- sary; and as the use of soda at the rate commonly recom- mended nearly doubles the expense of the spraying mixture, we have not recommended it, although the claim that when sal-soda is used it is possible to tell when the arsenic is dis- solved, is correct." The only trouble with this mixture seems to be the danger of an incomplete union between the lime and the arsenic, so that the full forty minutes' boiling, possibly even with .more lime and the addition of lime when diluting, would probably render the mixture entirely safe. Arsenic, Soda, and Lime. — This is often known as the Kedzie formula, as it seems first to have been recommended by Pro- fessor Kedzie, of Michigan. The method of its production is fully described in the following letter from Professor Kedzie: Agricultural College, Michigan, September 5, 1899. The formula I recommended for an arsenical spraying mixture to take the place of Paris green was the following : Boil two pounds of white arsenic with eight pounds of sal-soda in two gallons of rain water. Boil these materials together in any iron pot not used for other purposes ; boil them fifteen minutes, or until the arsenic dissolves, leaving only a small muddy sediment. Put the solution in a two-gallon jug and label Poison, Stock Material for spraying mixture. The spraying mixture can be prepared when- ever required in the quantity needed at the time, by slacking two pounds of lime, and adding this to forty gallons of water ; pour into this a pint of the stock arsenic solution ; mix up, stirring thoroughly, and the spraying mixture is ready for use. The arsenic in this mixture is equivalent to four ounces of Paris green. — 24 — Advantages of this Method: First— It is very cheap and the materials can be found in every village in the State ; Second— The stock material (arsenite of soda) is easily prepared and can be kept in that form for any length of time, ready for making a spraying mix- ture of lime and water ; Third— The arsenite of lime in the quantity required for spraying will not burn the leaves, or injure the trees or plants ; Fourth — It will be uniform in quality and not vary in strength, as Paris green often does ; Fifth— It makes a milky colored spray and the color on the trees will show how evenly it is distributed. Every one using such deadly poison should bear in mind the possible danger from its use; the pot, the jug, and every apparatus for making the arsenite of soda should be used for no other purpose of any kind. Yours faithfully, (Signed:) R. C. KEDZIE. Mr. Smith, of Hood River, Oregon, varies this formula, recommending: "Instead of two pounds of lime I used not less than six pounds; and I found that the additional lime pre- vented burning foliage and also retained the poison longer on the trees. I also used one quart instead of one and a half pints of the arsenic to fifty gallons of water." And again, "I would recommend using freely of the lime up to say ten pounds to fifty gallons of water." Danger from the Use of Arsenical Mixtures. — It should be borne in mind that arsenic is a very dangerous poison and that in any form it may be fatal to man or animals; especially should care be taken in the manufacture of the home-made compounds, as the handling necessary in these cases increases the danger from poisoning through carelessness. Properly handled, arsenic is perfectly harmless, and there is no excuse for any one becoming in any way affected by it. There is in the minds of a few people some apprehension that bad results might follow from the use of fruit protected by spraying; but this apprehension is certainly without foundation. There is yet to be the first case of injury resulting in this way. In all reported cases that have come under our observation the symptoms were in no case anything like those that might be produced by the arsenic. It is, nevertheless, true that a certain amount of arsenic remains on the fruit, and that no one sprays any considerable time with the arsenites without getting some of the material into the mouth or lungs; in some cases even enough to be recognized in the excretions. We have known a few cases in which the person applying the poison was careless — 25 — enough to become very slightly affected by the symptoms of chronic arsenic poisoning. These cases simply show the need of great care in handling the poisons, though this can be done with perfect safety when care is taken. Other Methods of Fighting the Codling-Moth. Before the introduction of Paris green for the codling-moth a number of methods were more or less generally used for com- bating this insect. The Band Treatment. — Foremost among these was the band treatment; this became generally discarded, however, for the reason that sufficiently satisfactory results could be obtained by the use of the poison alone, and that when this was used the amount of added protection offered by the use of the band method was not sufficient to counterbalance the cost of apply- ing the bands. Of late years, due to less satisfactory results with the Paris green, interest in the band treatment has been revived and not a few orchardists are using the two methods together. The band treatment consists in applying around the trunk of the tree, or on the larger branches, a band made of a part of a grain sack or other similar material which affords, in its folds and between it and the bark, very attractive places for the insect to hide when ready to transform into the pupa stage. After bands are applied it is necessary to examine each at least once in two or three weeks, and to destroy by hand all the larvae and pupse found in them. This is a somewhat tedious operation; it requires a great deal of time to get over a large orchard, and there seems to be a considerable danger of overlooking some of the insects. Again, the operation must be continuously attended to, or the results will be worse than though the bands were not used at all, because they afford such favorable hiding-places that the codling-moth is very much more apt to escape birds and other natural enemies. Some orchardists have adopted the plan of removing the band, killing the insects that are on the bark, and replacing it with a new piece of cloth, the old bands being gathered in a wagon and taken to a place where they can be thoroughly disinfected by running through a wringer, by the use of heat, or by means of chemicals. This method would seem to increase the proba- — 26 — bility of thorough work and probably greatly increase the speed and, therefore, cheapen the process. It is still a question whether the band treatment is worth the trouble when the Paris green spray is properly used; but it is altogether likely that when the Paris green is doubtful in quality, or from other causes unsatisfactory results are being obtained with the poison, it would well pay the cost of the treatment. Destruction of Windfalls. — Next to the band treatment the most favorite remedy in the olden days was provision for the daily destruction of the windfalls, whereby a large proportion of the worms contained therein would be destroyed before they left the fruit. One of the simple methods of accomplishing this was the use of sufficient droves of hogs in the orchard to keep the windfalls eaten up ; others made a practice of gather- ing the apples daily and making them into cider, which will accomplish the death of the worms contained. When it was not feasible to make the fruit into cider the destruction of the worms was accomplished by placing the apples in barrels, covered with a wire mosquito net. This, however, will not entirely prevent the escape of the worms, so the addition of a quantity of grain sacks above the apples, and, perhaps, a band around the outside of the barrel, might cause them to pupate in these traps. We think there are a few who still practice the destruction of the windfalls for the codling-moth, but like the band treatment there is a great deal of doubt if the process is profitable when the poison is used; used alone it certainly does not protect the crop as well as even a poor spraying of poison. If the utilization of the windfalls will pay for the cost of their gathering, there is no doubt that it will aid in the protection against the codling-moth. Destruction in Storage Houses. — A great many apples go into the fruit-house with the worms in them in various stages of development, and these escape and transform into their perfect adult condition in the fruit-house and then fly back to the orchards to continue their work. By some simple expedients, such as the use of screens over the windows, a great majority of them can be kept within the house and starved to death, with a corresponding advantage in the protection of the succeeding crop. — 27 — Traps. — A great many traps have been devised for the destruction of the codling-moth. They have generally been in the form, or some modification, of the band. Most of the traps have been proprietary devices and have had but little use, chiefly on account of the expense attendant upon their appli- cation. The plan which seems to be the most feasible is to place a band upon the tree over which, at a short distance, there is placed a covering of wire net; the idea being that the worm can pass readily through the meshes of the net, will hide beneath the band, there go through its transformation, and the moth produced will not be able to make its escape. At best, the use of these traps cannot be more effective than the use of the simple band alone, so that they will not be satis- factory if used alone. It is possible that when used with the arsenical spray they may be a supplementary procedure, which will be as effective and possibly cheaper than bands with their regular visitation. Other forms of traps have been devised; such as, for instance, lures for the moth, viz: lantern traps, sweets, etc.; but there seems to be no evidence that any of these have been of the slightest value, since the codling-moth seems to be very little attracted by anything that has been tried for this purpose. Scraping the Bark. — The practice of scraping the bark in the winter and the destruction of the insects attempting to pass the season upon it has been used to some extent. The difficulty in this method is the fact that only a small proportion of the insects pass the winter on the bark, so that while many may be killed, the practice alone will accomplish but little. Winter Sprays. — There have been many spraying mixture's advertised as effective against the codling-moth, which are to be applied in the winter time. These are only referred to here to call attention to the fact that they can be only of the slightest value, and are chiefly used by those having complete ignorance of the life history of the insect they desire to combat. Another similar insect in this State which attacks mostly stone fruits, the well-known "peach moth," can be to some extent controlled by winter treatment, but the habits of this insect are essen- tially different from those of the codling-moth. — 28 — Mistakes Commonly Made. All of the trouble with the codling-moth is certainly not due to the character of the Paris green. A great many orchardists, even in this State, have no very clear idea of the action of Paris green, nor of the methods of its application. It will be well, therefore, to point out some of the most common miscon- ceptions and causes of failure. One Application Not Enough. — The fact that most of our scale insects can be sufficiently controlled by one application seems to have fostered the idea that all insects can be con- trolled thus easily. In very early fruit, the earliest pears for instance, there are many localities in the State where one appli- cation at the proper time may be all that is needed, but in most situations, and always upon late fruit, repeated spraying during the summer, at three or four weeks apart, according to the locality, will be found necessary in order to obtain the best results. In the case of scale insects, the insect is upon the plant and exposed to the action of the insecticide all the year, but the codling-moth can only be killed during a very small part of its life; that is, between the time of the hatching of the egg and the entrance of the worm into the fruit. Now the period of egg-laying varies very greatly; but, as a usual thing, occurs not far from the close of the blooming period, so that the first crop of worms can usually be destroyed by an application made just as the petals are falling. In almost, or quite all of our apple and pear regions, the codling-moth has many broods; and in the latter part of the year, because of the different length of life of the different individuals, egg-laying is almost con- tinuous, so that it is essential, especially toward the latter part of the year, to maintain continuously a coating of the poison over the fruit and foliage. This requires repeated sprayings, and especially so in the latter part of the year. Sprayings Must Be Uniform. — Lack of uniformity in spray- ing will result in leaving too much of the plant poorly protected, and so greatly increase the danger due to the codling-moth. Irregularity can occur in three ways: First — In the spraying, unless care is taken, parts of the plant will not be sufficiently wetted. This is likely to occur — 29 — in the case of tall trees near the top, and in large trees toward the center. There is generally a sufficient number of codling-moths about to do a large amount of injury, so that the poor spraying of a part of the tree is very liable to result in a great deal of loss from the moth. Spraying should be looked upon as an operation requiring the most careful and conscientious work, and only those capable of working in that way should be permitted to hold the nozzle. Second — Too much spraying is as bad as too little spraying. Paris green is so heavy that, if one continues to spray a leaf after it is thoroughly wetted, in such a way as to cause the minute drops covering the leaf to run together and accumu- late on the lower edge, or drop off, he is sure in this way to wash off a large per cent of the Paris green, or to accumulate it along the lower edge of the leaf, where it will be of scarcely any value. This fact emphasizes the necessity of care in spraying, in order that no part shall be oversprayed before the other parts are sufficiently treated. Third — Care must be exercised at the pump to insure the constant stirring of the mixture, on account of the weight of the Paris green, which causes it to settle very rapidly. Without care in this regard one will be applying at one time almost pure water, and, at another, two or three times the proper strength of Paris green. Not only is such carelessness likely to result in injury to the tree, but will greatly diminish the effectiveness of an application. Differences in Location. — The fact is not generally appre- ciated that the habits of the moth are very different in different localities, so that the plan of procedure, especially the time and number of applications necessary for effective work, will vary in different regions. There are a few regions immediately adjoining the coast, where it seems possible to produce apples with but little codling-moth injury year after year, without any attempt at controlling the insect. There are regions in which the early spring application (that is, the one that is applied at blossoming time) can be dispensed with without any loss; again, in other regions, a failure to attend to this first applica- tion will conduce to a very great loss. Some of the complaints made against Paris green have been due to a failure to recog- nize these differences of habit in different locations, and the 4ub — 30 — attempt to follow blindly the practice of one region in another, in which the moth shows very different habits. Differences of Season. — There seems to be a very great deal of difference in the habits of the moth from year to year in the same locality. In Berkeley, for instance, while during some years only a small amount of injury will occur, even with no spraying, during other years a large proportion of the fruit will be wormy. Some of the complaints against Paris green are undoubtedly due to the fact that orchardists have been successful with one line of procedure during one season, and have followed the same program in the succeeding sea- sons with less success. The proper practice, therefore, in any locality, would seem to be the one which would insure good results in the season most favorable to the moth, even though it involve a little extra cost on the other seasons. We are not yet well enough acquainted with the effect of the character of the season upon insects to predict the result with much cer- tainty; therefore, it would be well always to be on the safe side. Importance of Treating the Codling-Moth. Where apples and pears are grown for home consumption simply, and where the codling-moth is not excessively abundant, it may be all right to neglect treatment, for under these circum- stances the fruit is usually produced in superabundance and the presence of a considerable amount of wormy fruit is not particularly objected to, since most of it can be fairly well utilized. Whenever these fruits are grown on a commercial scale, however, the subject becomes a much more important matter. The presence of any considerable quantity of codling- moth will seriously decrease the quantity yielded, and may make all the difference between success and failure. Wormy fruit also will never bring on the market a price comparable with that of sound fruit, though the cost of grow- ing, picking, packing, and shipment is the same. The efforts made by the fruit inspectors to drive wormy fruit from the market are entirely commendable, and it will be but a very short time before such fruit is absolutely unsalable. No orchardist can afford to produce any large amount of wormy fruit, even if the cost of treatment were equal to the profits accruing from such treatments. With proper methods, suffi- — 31 — cient care, and persistence, there is no doubt whatever that the injury from codling-moth can be reduced to a very small percentage. The Correct Practices for Treating the Codling-Moth. No simple directions can be given for the destruction of the codling-moth, which will be applicable in all fruit-growing regions. The correct practice in this, as in all other practices on the farm, is that which will produce the maximum profit with the minimum expenditure. The time of making the various applications, and the number of applications, and the need or uselessness of additional pre- cautions, will depend upon the locality and can only be learned by a study of local experience, and by practical experiment by the orchardist. There are some general principles that can be laid down to guide in the proper selection of methods of treatment. Time of Application. — The first application should be made in most localities within a short time of the blossoming period. In those places and with those varieties in which all the blossoms open out about the same time, the application should be made as the last of the petals disappear. When the blossoming is slower, so that some fruit will begin to form before the last is out of the bud, it may be necessary, where the codling-moth is bad, to make an application in the midst of the blooming season. If possible, however, the tree should not be sprayed during the blooming, as the blossoms to be fertilized are likely to be killed, or prevented from setting fruit, by the action of the spray. This first spraying should be made in almost all regions, with a possible exception of the immediate coast, where there is some evidence that it can safely be omitted. The time of the subsequent applica- tions can only be determined by careful observation in the locality. Under ordinary circumstances Paris green will remain on the leaves, sufficiently strong for the protection of the fruit, for three or four weeks. Under favorable circumstances it may remain effective even longer than this; and on the other hand, a dashing shower of rain or high wind may entirely rid the trees of the protection afforded by the spray; — 32 — they should be then at once re-sprayed. There is danger to the tree if applications are made too often, for it is possible to accumulate the poison upon the leaves by repeated spray- ings, so as to seriously injure the foliage. For late fruit special care will have to be taken, because these require con- tinual spraying until late in the season, when the leaves, being old, are particularly susceptible to Paris-green injury. The great abundance of codling-moths at that time of the year makes the complete protection of the fruit imperative. Methods of Spraying. — In spraying for the codling-moth the object should be to thoroughly wet every part of the plant, for, as we know, the eggs of the moth are left indiscriminately on the leaves, and apparently at random, by the moth; and the young caterpillar that hatches from these eggs nibbles here and there on the surface of the leaves or fruit, as it wanders about in search of a hiding-place where it may begin its bur- rowing into the fruit. This hiding-place is almost always the blossom-end in the case of young apples or pears; after the latter are larger, so as to touch each other, the place where they touch affords a very satisfactory hiding-place. The idea should be to so thoroughly cover the plant with the poison that, no mat- ter where the caterpillar may attack, its first meal will be a poisonous dose. The young caterpillar appears particularly susceptible to poison, so that it is desirable that the first mouthful should be partly of poison. Now in order to place the largest amount upon the plant, it is essential to spray in the manner that will leave the maxi- mum amount of water upon the leaves when spraying is fin- ished; that is, to cover the leaves as closely as possible with the dew-like drops produced by the spray nozzle. If the leaf in this condition is shaken these globules of water will run together and part of it will drop off the leaf; or, if the spraying is continued so as to cause them to run together, less water will actually remain on the leaf than was there before. In spraying, therefore, it should be the intention to cover the plant very uniformly, using only enough pressure to produce a fine mist; or, if more pressure is desired, to keep the nozzle far enough from the tree, so that the water will come into con- tact with the leaves not as a stream, but as a mist, and the moment the drops begin to run together, so as to cause any — 33 — of the leaves to drip, the process should be considered com- plete. With proper spraying there should be scarcely any water on the ground, but practically all of it caught and retained by the leaves'. This brings out clearly the contrast between the kind of spraying which is best when using Paris green, and that which is the practice with the washes for scale insects. In the latter case, the harder the stream comes in con- tact with the plant, and more free the use of the spraying material, the more likelihood of thorough, satisfactory work. Spraying with Paris green can be done much more rapidly, and, therefore, much more cheaply than spraying for scale insects. The best form of apparatus to be used will depend in part upon the amount of work to be done; but very good results can be obtained with a small and cheap outfit. The nozzle that will give a uniformly fine mist should be selected. There should be sufficient hose and extension rods to thoroughly treat every part of the tree; and an arrangement to insure a thorough stirring of the Paris-green mixture — more thorough than is usually provided by the devices for automatic stirring. EXAMINATION OF PARIS GREEN AND SOME OTHER ARSENICAL SPRAYING MATERIALS. By Geo. E. Colby. The enormous increase in the demand for Paris green throughout this country has caused manufacturers to put upon the market materials which have been carelessly or hastily made. It is not an uncommon practice to use needless and excessive amounts of arsenious oxid in the manufacture of Paris green; or the finished product is often lower in this essential than is lawful in the State where made, hence this class of green must be strengthened by the addition of " white arsenic" (arsenious oxid). Thus Paris green, which at best is a variable compound, comes by these abuses to contain free arsenious oxid. In this condition this substance in spraying materials is ready and certain to injure and destroy foliage. The application of compounds carrying any soluble leaf- destroying matter is particularly dangerous in semi-arid — 34 — climates. From experience, horticulturists have learned that arsenical spraying materials are often unreliable and danger- ous, and for years they have been sending samples of their purchases of Paris green to this Station' for examination as to purit}^. The greater part of these examinations have been made with the aid of the microscope alone, and by it the sample has been declared fit or unfit for spraying purposes. This method has been, fully explained in the first part of this Bulletin (see page 13). Lately, within the last few months, manufacturers, wholesale druggists, etc., have seemed to realize that their goods (insecticides) will always be condemned by this Department if they show impurity upon a microscopic examination. They have, however, regarded this as insufficient evidence. Eastern manufacturers, therefore, have, through their agents, requested this Department that a " proper analysis be taken " of their goods; meaning thereby, that a chemical analysis be made. This would, according to their understand- ing of the matter, reveal the presence of a sufficient lawful quantity of arsenious oxid. At the same time, this request indicates an awakening interest on the part of the manufactur- ers and dealers, probably because they want information which will enable them to make their output of insecticides — Paris green in particular — acceptable* to all. It is to satisfy these requests that part of this work was undertaken. Pure Paris Green, also called Emerald green, Schweinfurt green in Europe, is an aceto-arsenite of copper and may be regarded as a compound of verdigris and Scheele's green (arsenite of copper), having this percentage composition: Copper oxid (CuO), 31.29; Arsenious oxid (As 2 3 ), 58.65; Acetic acid (C 2 H 2 2 ), 10.06. (Report of N. J. Agricultural Experiment Station, 1897, p. 408.) It is to be noted that Paris green usually contains very small amounts of moisture and sulphuric acid (S0 3 ), and that the arsenic may be in both arsemc and arsenious combination; also, that the copper may exist as both copper oxid (CuO) and sub-oxid of copper (Cu 2 0). But one essential quality of pure Paris green is that it is wholly insoluble in pure water. Free Arsenious Acid in Unobjectionable Samples of Paris Green. — An 1895 sample of green pronounced by microscopic test as good enough for spraying purposes showed a total of 54.10 per cent of arsenious oxid, and 3.50 per cent of free — 35 — arsenious acid. Another good green, obtained in the market in San Francisco this spring, contained 4.1 per cent of free arsenious oxid. Analyses of Objectionable Paris Green Containing Free Arsenious Oxid. The following analysis of a sample of Paris green manu- factured in New York City, by its composition, illustrates quite fully the objectionable ingredients usually found in one class of Paris greens which this Department condemns as unfit for spraying purposes. This sample, upon a microscopic exami- nation, was pronounced unfit for spraying trees and the chemical analysis more than justifies the conclusion. Analysis of Paris Green Manufactured in New York City. Per Cent. Copper oxid (CuO) 31.25 Arsenious oxid (As 2 3 ), combined __ 29.30 Arsenious oxid (As 2 3 ), free 23.60 Acetic acid _ 11.28 Sulphuric acid (S0 3 ) .23 Water (moisture) __ 1.31 Silica .10 Soda(Na 2 0) .77 Potash (K 2 0) trace. Lime(CaO) 10 Zinc oxid (ZnO) _ _ 58 Prussian blue .75 Total ..'. 99.27 The main objection to this sample of Paris green lies in the fact that nearly one quarter (S3. 60 per cent) of its weight is made up oifree arsenious oxid, completely soluble in hot distilled water. Of the sum total of the other ingredients which are essen- tially impurities, viz: the sulphuric acid, lime, zinc, and the Prussian blue, only the last named compound is, by its pres- ence, at all significant. This material is commonly used as an adulterant of verdigris, and while the amount of it in this Paris green is small (.75 per cent), it seems not improbable that it was used to give a greenish tint to the free white arsen- ious oxid. This particular case shows a combination of materials com- pounded and sold as commercial Paris green for insecticide — 36 — purposes, which cannot be recommended for spraying as it stands; its sale and use should be legally stopped. Of the same nature, and objectionable for the same reasons as given for the above sample, is a Paris green sent here by the owner of a large orchard who u cleaned the leaves off his trees" by spraying with it. This material contained 29.40 per cent of free water-soluble arsenious oxid; the total arsenious oxid amounted to 52.94 per cent; copper oxid, 32.60 per cent; besides the other usual components. Another Paris green condemned by microscopic test was found by analysis to contain 24.60 per cent of free arsenious oxid; total arsenious oxid, 55.13 per cent; copper oxid, 26.70 per cent, and a large quantity of sulphate of soda. The makers of this material claimed that it contained 64.0 per cent of arsenious acid and 20 per cent of copper oxid, and seemed to be very much surprised that it should have been condemned by the microscopic test. In June, 1897, a sample of Paris green was received from the Secretary of the State Board of Horticulture of California, in which the microscope showed considerable impurity and the sample was deemed unfit for spraying — it analyzed as follows: Per Cent. Moisture 2.00 Arsenious oxid, combined.- 42.27) Arsenious oxid, free ._ 6. 70S Copper oxid 27.93 Sodium sulphate 3.50 Acetic acid, sand, etc 17.60 Total 100.00 A similar green to the one just recorded came from San Francisco in March of this year. It contained impurities by the microscopic test, and upon analysis showed 8.10 per cent of free arsenious oxid; 40.17 per cent of combined arsenious acid; 28.06 per cent of copper oxid; 2.31 per cent of sulphate of soda. A remarkably coarse-structured Paris green with very large, heavy crystals and much impurity, showed by analysis to contain 9.10 per cent of free arsenious acid; 39.58 per cent of combined arsenious acid; 34.60 per cent of copper oxid, and 1.50 per cent of sulphate of soda; acetic acid and moisture, 15.22 per cent. Of course, this sample was condemned. — 37 — Aside from the injurious effects upon trees from the use of such Paris greens as described above there is another aspect of the case, viz : the fraud connected with the sale of such mate- rials. For, if from one tenth to one third of the weight of these materials is made up of free "white arsenic," worth only- one third as much as good unobjectionable Paris green, it is not difficult to see where, on ton lots, the manufacturer makes large unearned gains. For example, if a wholesale dealer obtains $240 a ton for his article and if it contains one fourth free uncombined arsenious oxid, it is a simple matter to see that he has an unearned gain of about 17 per cent. By the time the consumer has his small lot of such objectionable Paris green at 25 and 30 cents a pound, it becomes a very expensive material for his purpose. Fortunately for the farmer, the remedy for all this is prac- tically in his own hands, as pointed out in the first part of this Bulletin. He has only to procure two cheap materials — "white arsenic" and lime — and by simple processes combine them into an insoluble arsenite of lime— -an inexpensive, effective insecti- cide, which will not injure his orchard. Adulteration of Paris Green. This Station has never yet analyzed a sample of Paris green in which adulterants were added to the extent reported of foreign paint materials. This is also the experience of several Eastern experiment stations. In Germany the case is quite different, for much adulterated green is found containing barium sulphate, calcium carbonate, chrome yellow, iron oxid, lead chromate, etc. In part these materials are simple make-weights, while others are added in order to produce different desired tints of color. Examination of Some of the Newer Substitutes for Paris Gr^en. "ARbENOIDS." During the last year several samples of what are called "arsenoids" and described as white, or barium arsenite, pink, or lead arsenite, and green, or copper arsenite, by their maker, have been received for experimental purposes at this Station. 5ub — 38 — si White Arsenoid" or Barium Arsenite. — This material upon analysis was found to be of the following composition: Per Cent. Barium carbonate 44.05 Barium chlorid _ 13.05 Barium oxid _ 8.18 Arsenious oxid, free 27.64 Lead carbonate _ ._ 1.86 Silica... >. 20 Moisture ._ _ 4.00 Total 98.98 The only ingredient which might give this compound a value for spraying trees is the arsenious oxid. But all of this oxid is in such a condition that it is extremely dangerous to foliage, and practical tests have shown it to be so. Of the other com- ponents, the largest, barium carbonate, simply makes weight and adds nothing to its value. The same is true of all the other ingredients. Notwithstanding that this material is offered for a much lower price than Paris green, it can not be safely recommended. " Pink Arsenoid," or Lead Arsenite. — This material is lead arsenite, colored with some pink-colored aniline residue, and shows the following composition by analysis: Per Cent. Lead oxid (PbO)... 49.58 Arsenious oxid (As 2 3 ), combined 40.02 Arsenious oxid (As 2 3 ), free 3.24 Moisture _ 31 Organic matter from aniline residue; lead sulphate, etc... 6.85 Total 100.00 This compound cannot be objected to, and a practical test with it shows that it is perhaps but little, if any, more danger- ous to foliage than Paris green. It is sold for much less than ordinary green; this, when considered with the low content of free arsenious oxid, should recommend it. " Green Arsenoid, v or Copper Arsenite. — This compound is "dead" green in color, and under the microscope is seen to be a — 39 — mass of irregular, sharp crystals. It shows the presence of some soluble blue,* which often contains arsenic. It analyzes as follows : Per Cent. Copper oxid (CuO) 28.83 Arsenious oxid (As 2 3 ), combined 53.51) ^ ^ Arsenious oxid (As 2 3 ), free 7.82) Moisture - 2.77 Silica _ ._. 40 Organic matter derived from soluble blue; sulphate of soda, etc 6.67 Total 100.00 While this material contains the guaranteed quantity of arsenious oxid, and is cheaper than the common green, still it is hardly safe, as it stands, to use in this climate with its nearly eight per cent of free arsenious oxid. It appears from the foregoing record that of these "arsen- oids" the lead compound is the best; i. e., the least injurious. The copper compound is certainly promising, and if proper methods are followed in its manufacture it can easily be made a desirable insecticide. But of the barium compound nothing more need be said than that it is simply worthless. It is a grave mistake to put it on any market for the use for which it was intended. PARAGRENE. Another of the newer arsenical spraying materials is a patented article bearing the name "Paragrene." A sample of it has very lately been received for examination by this Sta- tion. The manufacturers of paragrene claim " that the article was very extensively used last year by planters and growers all over the country, and that it is free from the objectionable features of Paris green, as it does not burn or scorch the most tender foliage. It contains the required percentage of arsenic or any arsenious oxid. Besides this the article is considerably cheaper than Paris green." It retails at from 13 to 17 as against 25 or 30 cents per pound for Paris green. A microscopic examination shows that this sample contains besides the ordinary green a considerable quantity of sulphate of calcium (gypsum) and also many crystals of " white arsenic." The substance analyzed as follows: * Sodium triphenylrosaniline-monosulphonate. — 40 — Per Cent. Copper oxid (CuO) 23.46 Arsenious oxid (As 2 3 ), combined 17.52 Arsenious oxid (As 2 3 ), free.. ._ 23.08 Acetic acid __. 6.72 Calcium sulphate (gypsum) _ 19.31 Sodium sulphate 2.26 Sodium chlorid _ 25 Peroxidof iron 20 Water ..- _ 6.20 Total 99.00 Notwithstanding that the above composition complies in many particulars with the claim made for it in the Patent Office, the fact that it contains so much (nearly one fourth its weight) of free, water-soluble arsenious oxid stands against it. In this sample of paragrene the free arsenious oxid rates the same as in some of the most objectionable Paris greens. This article, therefore, must be rejected, as it will positively cause injury to foliage if used in California orchards. Summary. The results of this examination of Paris green and other arsenical spraying materials may be summarized as follows: First — That many Paris greens nowadays contain large amounts of free water-soluble arsenious oxid, the manufacture and sale of which should be discontinued, both because these materials have proven injurious and unsatisfactory in horti- cultural work, and because they constitute a very obscure form of fraud upon the purchaser. Second — That the microscopic examination of a Paris green affords sufficient evidence for rejecting it if it contains as much as 6 per cent of free arsenious oxid; and above this figure there is no question of the great value of this rapid and excellent test. Third — That adulteration in the sense of added foreign matter to Paris green (e. g., barium carbonate, calcium car- bonate and sulphate), is rarely practiced in this country, at least by the manufacturers. Fourth — That the newer spraying materials, from the evi- dence at hand, with the exception of the very injurious barium compound and the paragrene, will doubtless prove acceptable and cheap substitutes for Paris green, if the quantity of free arsenious oxid, especially in the green one, is better governed by proper methods of manufacture. c