October, 1924
INDUSTRIAL A N D E,VGINEERING CHE‘MISTRY
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Some Chemical Problems of t h e Insecticide Industry’ By J. K. Dickerson N I A G l R A SPRAYER
CO., MIDDLEPORT, N. Y.
HE whole insecticide industry is based on the constant and never-ending struggle of man to control or eradicate the pests preying upon man’s useful vegetation, plants and trees-ultimately that man may remain master of the earth and survive, actually that he may have plentiful.food, clothing, drugs, and delicacies, also that those spending their time and effort to produce these things with Nature’s help may profit by their labor, and that those consuming the goods so produced may enjoy the best quality that the earth produces, for which there is always a ready market. According to an entomologist, proper insect or fungus control consists essentially in using the proper materialinsecticide or fungicide or combination, as the case may be-in proper quantities, or by thorough applications, a t the time when the aforesaid insects or fungi are most SUSceptible to such control and before the plant, tree, or crop has been seriously affected. I n other words, the three main factors are proper material, thorough application, and the right time. Assuming this definition of effective control to be substantially correct, let us note (1) the importance of the chemist to the insecticide industry, from a manufacturing point of view; ( 2 ) what problems are now confronting us regarding the substances our chemists have produced to date for use in insect or fungus control; and (3) perhaps suggest some lines aldng which chemical research in this industry should be directed, as taken from the demands made on the manufacturer through trade channels.
certain percentages that conform to usual customs, laws, and label guarantees, but also to make sure that a stable combination has been formed which will assure safety and satisfaction in use and allow no deterioration with time and the ravages of the elements. Quoting calcium arsenate again, because that is a large item a t present, the writer has personally seen and analyzed over a period of time, samples of this product which when freshly manufactured contained 0.2 per cent of water-soluble arsenic, but upon exposure in a damp, warm climate where carbon dioxide was present in some quantities, this figure gradually and steadily rose daily to around 1 per cent a t the end of a week, 2 per cent a t the end of fifteen days, and eventually to nearly 5 per cent in the course of six or seven weeks. The same product from other sources, tested under the same conditions and during the same period of time, showed no deterioration whateverindeed did not after two or three years when tested later as a matter of interest. This assurance of stability, however, is very necessary in such products as these. Cos-After the control of the chemical combination according to formula or guarantee has been taken care of, the chemist, whether from the manufacturing, research, or government and experiment station viewpoint, is, or should be, very much interested in the cost of a given pr6duct. Our chemists are endeavoring to develop the most economical method of manufacture, which usually consists in gaining a maximum of production of standard quality with a given equipment. This entails a constant effort to improve the manufacturing processes with necessary changes in temRELATION OF CHEMISTTO INSECTICIDE INDUSTRY peratures, size of batches, rate of drying, rate of addition of PROPER MATERIALS-under this item, we find the chemist is ingredients, dilutions, etc. We are assuming that the equipconcerned from three angles-(a) chemical content, ( b ) cost, ment is efficient since that is a problem of mechanical nature and maintenance rather than a care of the chemist. The and (c) effectiveness. CHEMICAL CONTENT-The chemist is interested in the chemist, however, may find that a change in the rate or chemical content or make-up of insecticides and fungicides, style of mixing, for instance, or of drying, may give a better first for pure control reasong. Every manufacturer who product or the same product in larger quantities. The chemist may reduce the cost of a product by finding would produce a quality product must carefully check that product as it goes through his process, and this is particularly short cuts. Arsenic from the copper and lead smelters of true of the chemical reactions in the manufacture of given the Rocky Mountain states, and more or less all over the batches of insecticides and fungicides. Take calcium arsen- world for that matter, is shipped to a plant, say, in the East, ate, for instance. Perhaps some one has found a way to where it is oxidized by the use of nitric acid to arsenic acid. grind out batch after batch of this product, adding exactly This arsenic acid is then given another ride on the railroad equal or proportionate weights of lime and arsenic acid in to another plant, where lump lime from another more or exactly equal or proportionate amounts of water a t the same less distant source is slaked in a vat and the arsenic acid temperature during the same or proportionate lengths of added to it, forming calcium arsenate. This calcium arsenate time, but such is not the case a t this plant. The discrep- then takes one or, more likely, two or three more rides, ancies in the purity of succeeding batches of lump lime, for again one-half or two-thirds of the distance across the contiinstance, in this case is enough to cause excessive variation nent, and eventually, through trade channels and dealers, in the total arsenic content of different batches, and so every becomes available to a cotton planter for killing his weevils. batch that is mixed must be checked by itself and adjusted Would it not be of great advantage to the consumer, who if necessary. This is mechanical routine work but very neces- is the ultimate lord of the situation, if arsenic or any other ingredient could be combined directly with the other masary. Materials used for insect and fungus control are almost terials required a t a convenient and geographically sensible invariably chemicals or chemical combinations of some kind, place and made quickly available for the proper trade and their manufacture is thus subject to this kind of chemical channels? Let us bear in mind in working out improvements in our control or manufactured under chemical supervision. There is another angle to this control work which is highly industry that almost without exception no chemical process important and that is not only to make a combination with or idea is worth much unless it makes a given product better a t the same cost, the same product at less cost, or a similar Presented before the Division of Agricultural and Food Chemistry or competing product of equal efficiency or greater adaptat the 67th Meeting of the American Chemical Society, Washington, D C , April 21 to 2 6 , 1924. ability a t an equal or smaller cost. In other words, a chem-
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‘INDUSTRIALAND EATGINEERING CHEMISTRY
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ical improvement to be an improvement of value to its sponsor must contain a commercial advantage of some kind. EFFECTIVESESS-After concerning himself with the chemical content control, and with the cost of insecticides and fungicides, the chemist is interested in the general field effectiveness of a product, because an extremely effective material of high cost may be much more economical than a cheap product of low efficiency. Here we seek to kill the highest percentage of pests with a minimum consumption of materials and labor. We here have to ask help from the horticulturist , entomologist, and plant pathologist to interpret the results and gage the effectiveness of a given material. The efficiency of a given material includes its lasting effect-that is, its ability to kill succeeding generations of pests, a quality partly described by our common term, “sticking” qualities. A product will usually be more effective if its control is complete for 10 or 15 days after application, than if it lasts only 2 or 3 days. I n addition to the qualities mentioned, a product to be effective must be readily obtainable, handled without great difficulty by the operator, and in general usable by fairly well-known or standard practices or in standard equipment. Of course, there are many special conditions which require special treatment, but this is a busy world and the cotton planter, the vegetable and fruit growers, and the farmers are not interested in anything that takes great preparation, skill, or knowledge to apply. Finally, the material must not harm the plant or tree upon which it is used. This might be called the item of safety and is gained largely by the control of chemical combinations .exercised by the chemist during manufacture.
THOROUGH APPLICATIONS The connection of the chemist with the materials used for insect and fungus control is his. main interest in control, but he has some duties also under the other two requirements: First, the proper materials made by him must be applied in proper quantities or by thorough applications; and second, this application must be made at the right time. The problem of making thorough applications is judged largely by the entomology and plant pathology departments, and is also related to the item of effectiveness. The chemist, however, is invaluable in checking amounts of materials used, which are later found remaining on foliage, stems, bark, or even on the ground. I n this way he helps to ascertain the lethal dose, and if necessary analyzes the dead bugs to find how much is inside them as well as how much they left behind. The chemists’ figures show the evenness of application, a quality which is partly expressed by our common understanding of “spreading,’ capacity or quality of insecticides and fungicides. I n short, the chemists find the facts from which results are interpreted. Another duty often performed by the chemist needs a word of caution. Many plants making and selling these products employ a chemist or two for plant control and research work but no other scientists, and so the chemist is called upon t o write labels, not only to give the chemical ingredients and guarantee, but also the recommendations for its use; perhaps still further to assist in preparing the copy for advertising material which contains recommendations and directions for using the products. I n such cases it is essential that the chemist be familiar with the field problems and pests to be treated. TIME
OF
APPLICATION
The chemist may help other departments decide the most advantageous time of application by determining the residue on foliage and other parts of plants after different lengths
Vol. 16, No. 10
of time, after day and night applications, under conditions of dew and rain, calm and breezy weather, bright and dull days, etc. He will, however, let others count the bugs killed at these times and tell him whether they are really dead or merely sick, later to return to do further damage. UNSOLVEDPROBLEMS The fact that there are problems, and many of them, for the chemist in this industry proves that to date he has not produced entirely satisfactory materials for control work and that the entomologist and other plant scientists have not so far been able to get the control desired to maintain our superiority over our most numerous enemies. CHEMICAL CONTENT Taking the factors of materials in the same order in which we discussed the chemist’s relation to them, let us consider the chemical content or make-up of our materials. Are they all that might be desired? Probably not. For example, water-soluble arsenic is present in every commercial insecticide that contains arsenic as a killing agent and, under the proper conditions which furnish the water to dissolve it, is rapidly absorbed into the plant tissues .and in many cases seriously burns the foliage, perhaps spoiling the crop or killing the plant or tree. Such severe burning is rare a t present with arsenates, but was quite general at one time during the more extended use of arsenites or poorly made arsenates. Experiments with calcium arsenate have indicated that an amount of water-soluble arsenic less then 0.75 per cent will not injure most plants, such as cotton, most vegetables, and some fruits, excluding stone fruits. Why not make calcium arsenate, then, with no water-soluble arsenic and be entirely safe? As our plants are now constituted this would be a commercial impossibility. Our arsenic acid is made to contain a minimum amount of free unchanged Asz03, but there are always traces, forming probably slight traces of calcium arsenite. Moreover, calcium arsenate is also very slightly soluble in water, which accounts for most of the remainder. But some one has also come forward with the theory that a little water-soluble arsenic increases the killing power of an arsenical-getting the comparison, no doubt, from the effect of, say, Paris green and lead arsenate or calcium’arsenate, and comparing the water-soluble content of the two, one of which may be 2 per cent and the other 0.2 per cent. The writer has seen no scientific or experimental data on this subject, however. So we make arsenicals with as small amount of water-soluble arsenic as commercially feasible, usually about 0.2 per cent, until some chemist shows us reasons for more or less in the future. Sulfur and lead arsenate are often used together in liquid ~iolutions,and are far from an ideal combination, especially when left to stand for some time, as often happens. Some of the products manufactured and marketed for insecticide and fungicide purposes are subject to deterioration on storage. To prevent this deterioration, therefore, becomes one of the problems of the insecticide industry. Unfortunate results from some of the early attempts to use the original high total and soluble arsenic calcium arsenate have greatly discouraged its use. COST
The cost of control is regarded as a chemical problem. We are all familiar with the most common forms of control of San Jose scale with lime-sulfur solution and other polysulfides, with calcium arsenate for the cotton boll weevil, etc., but there are other pests and diseases which are very
October, 1924
INDUSTRIAL A N D ENGINEERING CHEMISTRY
prevalent and are not controlled to any extent because the crops will not bear the expense, or a t least the growers as a body are not as yet convinced that they will. The chinch bug on corn and the pea aphis are real pests. The chinch bug can be controlled by calcium cyanide, and the pea aphis can be controlled by nicotine, but many growers consider that the cost is high in comparison with average results. Many alfalfa farmers in the West would control the alfalfa weevil's ravages but for the cost of arsenical spraying or dusting, which they usually consider higher than the damage warrants. Yet the time is probably soon coming when these crops will have to be protected, and if we are not ready with the suitable cheap protection, then peas, corn, and alfalfa will be higher in price for somebody to pay for what the weevils, aphis, and bugs destroy. Mildew on clover and smut in grains are serious and are only very partially controlled. The list of other uncontrolled pests and diseases is too long to enumerate here. There is nothing new or startling about these things. They are here and are growing in the intensity of their damage each year. They come in the present classification of fungus, chewing and sucking insects, and weevils that we know how to control with copper sulfate and sulfur, with arsenicals, and with nicotine, but all these materials with the exception of sulfur are too high to buy for general use. This might not seem such a crying chemical problem to the laboratory chemist, but let him spend one week going among the farmers, cotton planters, and vegetable growers trying to sell perfectly legitimate insecticides and fungicides for which there are crops in need on every hand, and in nine cases out of ten he will be told that the need is acknowledged but the cost is too high, and the farmer will take a chance of getting a crop without protection. Probably not over 5 per cent of the cotton is protected from the boll weevil, and in the finest fruit and vegetable-growing sections the percentage of protected area is surprisingly small. Cost of materials] then, is one of the great problems which we face and will be a hard factor to surmount. However, with the enormous chemical resources and activities of this country, there is reason to believe that the ultimate cost of protection of crops, as this protection becomes more general, will gradually diminish.
EFFECTIVENESS On the score of effectiveness of materials we have by no means reached the ultimate goal, perhaps partly from a lack of understanding of how some of our materials produce a given result. For instance, sulfur is a great fungicide, but in most cases we lack knowledge of how it works, whether by contact, emission of sulfur dioxide gas, or by an acid effect, also whether it kills spores or germs. As previously suggested, water-soluble arsenic should be studied further, as we also need to know more of the chemistry and workings of Bordeaux mixture. The fineness of dust materials is another interesting problem, and until we know something definite about the subject, we go on assuming that the finer the material the more effective it will be. Our usual specification that dust materials must pass at least 95 per cent through 200 mesh is a very crude check on quality, because we must go far beyond 200 mesh before the particles begin to be fine enough to form an efficient dust. A requirement through 400 or 500 mesh would be much nearer the point of efficiency, but the finest screens made, it is believed, are 350 mesh and these are too fragile for serious use. The question of stickers and spreaders has received much attention of' late and it is hoped that in the future we will not need to use such a large amount to produce the same effect. Recently, we have heard considerable about the electri-
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fication theory on arsenicals. There must be some basis for the belief that arsenicals given a positive charge in some way during the process of dusting are attracted by the slight negative charge alleged to be present on the plants, enabling the arsenical to be retained by the plant in larger quantities and more uniformly distributed, giving greater control. Further light on this subject will be welcome. We are in need of more lasting effects of insecticides and fungicides. We do not want to dust or spray seven or eight times in a season if it can be done with equal effectiveness in some way with two or three applications. No doubt this angle will constantly be improved. The safety factor must not be forgotten. Our insecticides and fungicides are not only not foolproof, but they are too much affected by weather conditions, etc., whereby a standard product might sometimes cause injury. When we find that in some cases our old standard lime-sulfur solution causes defoliation on apple trees as high as 30 per cent and that only a year or two ago only about half the calcium arsenate used in the South passed Government specifications entirely although most of it was used, we are deeply concerned. This same calcium arsenate did not in most cases do any harm, owing to favorable weather conditions, while on the other hand a perfectly standard product has been known to burn quite severely under adverse conditions. Unfortunately, we cannot control weather conditions and so will always have to reckon with them in our control work. Such problems might be enumerated indefinitely, but enough have been given to indicate the need of further research and experimentation.
SUGGESTED RESEARCH Briefly, in closing let us consider some of the things that are desired and note the known means of arriving a t the desired ends. We must have better control work to keep materials standard to avoid injury and dissatisfaction among the consumers. This is a laboratory responsibility and there is no reason for shirking it, because we do not lack knowledge of present specifications. To reduce the ultimate cost to the consumer we must do one of two things-reduce the cost of raw materials (manufacturing costs are not excessive and are indeed small in proportion to the materials costs a t present) or attain the same result by making the same materials of the same cost more effective, go farther, or have greater lasting effect. Chief among the materials which are objected to because of their cost are arsenic and nicotine. Perhaps these articles can be replaced by other materials of less cost, but this is not expected for some time. However, we will probably have to learn how to obtain these a t less cost, and it is not a wild guess that eventually the results for a given cost will be double what they are today. I n this country we know how to increase efficiency of mechanical and chemical manufacturing processes and are doing it every day. The same thing must be done to the application processes aided possibly by other ingredients or factors which are now in question. There is always a last emphasis on the safety factor, because a dead tree produces no fruit. Let us, then, use all our present knowledge in the quest of the greater efficiency which is the hobby of the American people. We know what to do for most pests, but we do not do it well enough, and the present cost is excessive. But by chemical research and cooperation with entomologists, horticulturists, and plant pathologists, there is no doubt that man will triumph over his most numerous enemies and have all that he wants to eat, drink, and wear from vegetable and plant sources.
