Application of Insecticides Old and New Methods R. D. Glasgow New York State Science Service, Albany, N . Y . whisk brooms and sprinkling cans were used to apply arsenicals before 1870. Bellows and gravity sprinklers and dusters speeded up the application of insecticides until hand pumps, and then steam- and gasoline-powered pumps, were devised. Modern equipment for the applica,tion of insecticides includes both fixed-wing planes and helicopters for spraying and dusting fields, multinozzle trucks for spraying orchards, and thermal-aerosol generators for fogging large areas. I
T
H E development of economic entomology has been a peculiarly American contribution to human welfare, largely, perhaps, because in Europe the insect-vs.-human complex, through long association, had arrived at a state of fairly effective biologic balance; whereas in America old-world crops encountered new insect enemies, while old-world pests, transplanted without their old-world enemies flared into catastrophic numbers. Since Linnaeus, European and early American entomologists have been diligent in the collection, description, and classification of insects, and a few concerned themselves with the life history and habits of injurious species; but prior to 75 or 80 years ago, little progress had been made in the development of effective insecticides, or of the methods and mechanisms for their application. Before 1870 the recommended insecticides were limited in number, and with few exceptions not especially effective; the methods of application were primitive indeed.
The insecticide value of pyrethrum (as Persian insect powder) and of tobacco was well known, but the insecticides then commonly recommended consisted chiefly of such things as lime, Scotch snuff, red pepper, road dust, whitewash, soapsuds, and home-made decoctions of hellebore, quassia chips, pyrethrum, tobacco, and the like. The state of current knowledge concerning insecticides of that comparatively recent period is well expressed in an editorial in the Practical Entomologist for October 1865: The agricultural journals have from year t o year presented through their columns various recipes as preventive of the attacks, or destructive t o the life of the curculio, the apple moth, the squash bug etc. The proposed decodions and washes we are well satisfied, in the majority of instances, are as useless in application as they are ridiculous in composition.. . .
~~~l~ Models of BellowsOperated Dusters and Sprayers (6)
INCEPTION
Primitive Equipment Used a Generation Ago (3) Left, heath whisk, the first deviise used to apply Bordeaux mixture; r i g h t , an improved brush designed to be connected by a hone to a reservoir, carried knapsack fashion by the operator.
The really effective control of insect pests probably should be dated from the first usage of arsenicals for control of gnawing insects (about 1869),and of kerosene emulsion for control of sucking insects (about 1875), and, counting from the crude methods and equipment of that relatively recent period to present methods and equipment, progress in the development of better insecticides and more effective and economical methods and equipment for their application has closely paralleled the progress that has characterized almost every field of human interest during the past three quarters of a century. The use of arsenical poisons in quantities dates from the rather sudden appearance of the Colorado potato beetle as an economic problem of alarming magnitude. This insect, native to the semiarid West, where it had previously fed on wild solanaceous plants, found the potato a particularly acceptable Bource of food when the westward spread of potato culture brought that important crop plant within its reach. Thereafter this new fashioned potato bug spread rapidly eastward to the Atlantic seaboard; its apgearance was viewed by potato growers everywhere with extreme alarm. I n the Prairie Farmer of August 1863, C. V. Riley published what appears to be the first description of the eggs and larva of this insect. 675
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676
An Early Traction-Powered Sprayer ( 4 )
Earlier, the new fashioned p o t a h brig \vas laboriously jarred from the potato plants into pans of kerosene. Dusting with ashes or sprinkling with hellebore was recommended for its control. Then someone, whose name no one seems to know, tried Paris green; this proved effective and its use spread rapidly. At first, this poison was mixed with water arid applied wit,h a sprinkling can or with' a whisk broom. I t was about this time that crude sprayers were developed. On May 28, 1869, a George Liddle o! Fairplay, Wis., w o t e to the editor of the Galena, Ill., Gazette that if one mixed 1 pound of Paris green with 2 pounds of flour and sifted it through t'he meshes
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of a coarse muslin bag onto the potato tops early in the morning while the dew was on, the larvae would drop to the ground by thousands. He stated further that 3 pounds of the mixture would treat an acre of potatoes. Soon efforts were made to develop practical insecticide dusters of various kinds. Paris green was used successfully in 1873 for control of cankerwornis in a few Illinois orchards. In 1878 after application of Paris green for control of cankerworms in an orchard in Niagara County, N. Y . , i t was observed that the apples on the sprayed part of the orchard showed less injury by codling moth than the apples on the unsprayed parts of the orchard. This observation was confirmed in Michigan in 1880, and arsenicals rapidly came into general use for control of gnalving insects of many kinds. Then began a series of efforts to improve both insecticide materials and mechanisms for their more effective, more convenient, an{ more economical application. Paris green was eventually displaced by the more insoluble and safer lead a senate which, as late as the turn of the century, was still prepared by mixing chemicallv equivalent solutions of sodium arsenate and lead acetate. Then came commercial lead arsenate pastes, and finally the highly dependable, finely powdered dry lead arsenate of today. Calcium arsenate for dusting cotton, as well as various other crops, also came into extensive ube. * Recently, newer, and almost unbelievably potent insect killing chemicals, such as DDT, benzene hexachloride, chlordan, and the like have been added to our armament against insect pests. The development of insect control procedures and practice and the mushrooming stature of applied entomology are vividly expressed in terms of the reported 60,000,000 pounds of arsenical insecticides produced and used annually before the war, and the present annual production capacity of 100,000,000 pounds for the single insecticide, DDT. The several billion gallons of insecticide and fungicide sprays and billions of pounds of diluted dusts used each year present a huge market and an incentive for the development of better insecticides and methods and equipment for their application. EARLY METHODS AND EQUIPMENT
By comparison with present day equipment the earlier devices employed for the application of insecticide and fungicide materials were almost unbelievably crude. Even the whisk broom was a useful tool at this stage, and continued to be the accepted means to grapes in France until as late as 1883. bellows sprayers were manufac-
A Knapsack Type of Gravity-Powered Sprinkler (4)
High Pressure Gravity Sprinkler, Powered by Elevation of the Tank (5)
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677
Aerosol fogs are of the following three general types: An oil solution of the insecticide is dispersed in microscopicdroplets by a liquefied gas propellent (usually Freon); an aerosol mist or fog is produced by mechanical means; or the insecticide solutionis dispersed by means of the thermal-aerosol fog generator, Of the latter, there are two principal types on the market: One discharges the insecticide solution or suspension as a relatively coarse spray into a jet of superheated steam delivered by a flash boiler of the tubular coil type; the other discharges the insecticide soluAn Early Hand Power Sprayer (left, 7). A n lmproved Sprayer U by Hand or by Tractin- P n w - w (*;oh+ ?\
is tempered t o the desired degree by the controlled admixture of cold air. I n either case, a portion of the suddenly heated coarse spray droplet is vaporized; this serves as a propellent to disrupt the less volatile remainder of the droplet into smaller droplets, the diameter of which is determined by the formula used and the temperature a t which the disruption occurs. F u n d amentally, the basic principle is 'substantiPROGRESS ally the same as By contrast with the whisk that Of the COURTESY D. 6 . SMITH & COMPANY broom and its crude contempoqroduced by the Old Method of Applying Poison o n Crops (left); Reproduction rary devices, there are now of First Hand Sprayer (center); New Type Sprayer ( r i g h t ) liquefied g a s beautifully designed and highly (Freon) disruptefficient hand sprayers and ing propellent. power sprayers of many kinds, combined sprayers and dusters The thermal-aerosol insecticide fog generator, regardless of backed by powerful blowers, airborne sprayers ranging from the design, is an outgrowth of the original Langmuir, and subsequent wartime specially equipped bomber jungle sprayer carrying an oil-fog screening smoke generators developed for, and used by the 800-gallon tank of DDT in oil solution and flying 200 miles an Army and Navy during the war. These military screening smoke hour, through the commercial flight service planes of various generators were built to deliver an oil fog, in which the droplet types, to the helicopter that can poise, or fly forward, sidewise diameter ranged between 0.5 and 0.75 micron; this is the particle or backward only a few inches above the crop or other objective. size that will give maximum dispersion of light rays within the The most notable recent development, perhaps, is the insectivisible spectrum. cide aerosol oil fog and mechanisms for its production. For insect control purposes, however, the best of these machines have been modified to deliver an oil fog, in which the mass-averI n September 1892, L. 0. Howardreported in Insect Life that the multiplication of mosquitoes could be checkedby a film of kerosene age droplet diameter may be selected at will, and the range of on the surface of mosquito breeding water. Light petroleum oils droplet diameters held within fairly narrow limits. are still used as a supplementary measure for cpntrol of these insects, but in 1930, Joseph M. Ginsburg produced the New Jersey mosquito larvicide, an emulsified fuel oil solution of pyrethrins. This larvicide is more effective than the unmodified oil film; it uses only one tenth as much oil and, consequently, offers greater safety to fish, aquatic birds, and vegetation. Later, in 1937, Ginsburg showed that outdoor audiences can be given several hours' protection from mosquito annoyance by space spraying with a dilute solution of his pyrethrum mosquito larvicide; this, without harm to grass, shrubs, trees, ornamental plants, man, or other higher animals. This innovation pointed the way to many recent developments in the use of various insecticidesprays, and particularly aerosol fogs for the destruction of adult mosquitoes, blaok flies sand flies, or punkies, houseflies, and $he like. Old Woodcut Showing Early Equipment Used i n Orchard Spraying (7)
tured; gravity sprinklers and dusters were devised. Some of the early efforts to develop orchard and crop spray outfits or dusting outfits would have delighted Rube Goldberg himself. Hand pumps were the rule on the earlier spray outfits; some of us have painful memories of orchard spray rigs so equipped. Soon, however, a few row-crop sprayers were equipped with a wheel operated chain or traction drive; these were quickly displaced by powerful steam- and gasoline-poweredpumps.
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1. Chemical. Both insecticidal and fungicidal activity increase with increase of exposed surface. The relation of droplet diameter t o the number of droplets and to total surface area, for 1 gram of water, is:
Type of Dispersion
Diam. of Droplets Mm. hZp
Approx. No. of Droplets
Approx. Surface Area Covered, Sq. Cm.
, 2. Rate of fall in still air for aerosol fog droplets varies with droplet diameter as follows:
COURTESY BELL AIRCRAFT CORPORATION
Modern Orchard Spray Outfit Equipped with BlowerReinforced, Rfultinozzle Assembly
Diam. of Droplets, Mlli~
Approx. Rate of Fall per Seo., In.
Bpprox. Time to Fall 1 Ft.
Approx. Time t o Fall 10 Ft.
100 10 1 0.1
12 0.12 0,0012 0.000012
1 sec. 1 . 6 6 min. 2 . 7 5 hr. 1 1 . 5 days
10 sea. 16.66 min. 2 7 . 5 hr. 115 days
3. Rate of fall in still air may govern the distance a droplet is carried by wind, when used out of doors. The distance carried by a 4-mile breeze while settling 1 foot will vary with droplet diameter : Droplet Diameter, Mfi 100 10
1
0.1
COURTESY HARDIE MANUFACTURINQ COMPANY
Modern Orchard Spray Outfit Equipped with Multinozzle Spray Boom
COURTESY JOHN BEAN MANUFACTURING COMPANY
Helicopter Dusting Cranberry Bog
This control of droplet diameter, or of particle size, is essential because different types of insect control problems require aerosol fogs of different characteristics, associated with different massaverage droplet diameters. [Data adapted from Gibbs (1) and Glasgow (e) are given in the following tables.] Some of these characteristics are:
3
Approx. Time to Fall 1 Ft.
Approx. Distance Carried While Settling 1 Ft.
1 set. 1.66min. 2.75hr. 1 1 . 5 days
5 . 8 feet 586.6 feet 1 1 . 1 miles 1111,l miles
These theoretical values are never encountered i s practice. Air is never still, even in enclosed spaces. Warehouses breathe in response to changes in barometric pressure; and thermal convection currents and obstacles keep moving air in a constant state of turbulence. An understanding of the relations cited, however, is of utmost importance in adapting aerosol fogs to their appropriate places in insect pest control procedures. Space fogging out of doors may be used to control flying insects, such as flies, mosquitoes, black flies, sand flies, punkies, and the like. Bleachers may be cleared of pests before a game. Fogs of pyrethrum or DDT may be used singly or in combination. Parks, lawn parties, and recreation areas may be fogged, even while occupied. Usually a very small droplet diameter should be used for best results, although some added residual effect may be obtained by a concluding switch t o a larger droplet diameter, For space fogging indoors aerosol fogs are exceptionally well suited for use as a substitute for gas fumigation in many cases. Here, the smallest available droplet diameter should be used. An insecticide such as hydrogen cyanide, methyl bromide, chloropicrin, or ethylene oxide in gaseous dispersion holds the individual gas molecules in constant motion a t high velocities; thus, searching out all openings, the molecules tend to escape rapidly by diffusion. I n an aerosol fog, even droplets as small as 0.1 micron, do not exhibit Brownian movement. Such droplets hang passively in the air, except for gradual settling in response to gravity, and do not have any tendency to escape by diffusion. For this reason, laborious and expensive sealing of windows and doors is unnecessary when aerosol fogs are used indoors. The thermal-aerosol oil fog, in its appropriate field, is one of the most promising methods for the application of insecticides. It merits careful study of its possibilities and limitations. For the past 2 years (the seasons of 1946 and 1947) more than 70,000 acres of salt marsh in Long Island have been sprayed from the air with a 1% solution of DDT in No. 2 fuel oil, used a t the rate of 2 quarts (0.04 pound) of DDT per acre, for the suppression
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of adult mosquitoes. The cost was calculated to average less than 16 cents per acre. Where there is a forest cover, however, or a dense cover of other vegetation, such m marsh elder (Zvaoraria), or the introduced fox tail, reed, or plume grass (Phragmites communis),so many of the coarser, mechanically produced spray droplets are screened out by the dense plant cover, that insects concealed beneath it are not reached effectively by the insecticide. By contrast, because the smaller fog droplets tend to follow the flow lines of transporting air currents, an aerosol fog of appropriate droplet diameter applied from the air with the usual downthrust should pass through a forest crown with little loss and with effective concentration as a long suspended space spray, or persistent fog beneath.
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LITERATURE CITED
(1) Gibbs, W. E.,“Clouds and Smokes,” London, J. & A. Churchill, 1924. (2) Glasgow, R. D., Mosquito News, 7,No. 1,22-7 (March 1947). (3) Lodeman, E. G., “The Spraying of Plants,” New York, MacmilIan Co., 191% (4) Riley, C. V., “Entomological Publications of C. V. Riley,” Jefferson City, Mo., Regan and Carter, 1873. ( 5 ) Riley, C. V., Fourth Report of the U. S. Entomological Commission, Washington, D. C., U. S. Govt. Printing Office, 1885. (6) Sempers, F, W., “Injurious Insects and the Use of Insecticides,” 1894. (7) Weed, C. M., “Insects and Insecticides,” published by the author, 1891. RECEIVED November 22, 1947.
Insecticide Industry’s Contribution to Food Production I
L. S. Hitchner
Agricultural Insecticide & Fungicide Association, New York,N . Y .
A
MERICAN farm history is a series pf cases in which a new quality and cleanliness by making it possible to keep dairy barns pest appeared, spread and devastated, and finally was and processing plants free from insect infestation and contaminabrought under control, more or less, by some chemical. tian. The National Livestock Loss Prevention Board has started The Bureau of Entomology and Plant Quarantine estimates that there are 80,000 kinds of insects in North America. At work in several midwestern states on the protection of cattle by least 5000 of these are known to have economic importance. the use of chemicals. Board representatives have traveled No accurate dataexist to show just how extensively through the cattle states pointing out the proved and tangible many of these are being systematically condollars and cents benefits-a 50-pound trolled with chemicals, but in the last Statistics prove that chemical annual report of that bureau there is mengain in weight per head, in a single season, tion of research and test work on less than is an inexpensive form on beef animals and comparable gains in of crop insurance. The United 200 insect species. Annual losses from inmilk yields from dairy herds. I n Kansas States has taken the lead in the and Oklahoma alone more than 2,000,000 sect pests in the United States are estiapplication of chemistry to the mated to average 2 billion dollars. cattle were treated last year with an esti- farm, but the relation of pestiIn the field of plant disease pests, the mated gain of 75,500,000 pounds of beef. cides to the food supply has now American Phytopathological Society estiChemists today are vigorously conbecome important to the world. mates that there are in the United States tinuing their search for new pesticides. 25,000 infectious plant diseases including One company tested more than 12,000 10,000 of known economic importance and chemical compounds in a ten-year period; many others potentially dangerous. The 500 leading diseases on of these, 10 were found to be promising for agricultural use. If the entomologist and pathologist would tell the chemist what major crops cost 2 billion dollars a year and the remaining diseases an equal amount-a total plant disease cost to the nation pests need to be controlled, and their characteristics and of 4 billion dollars. economic importance, specific chemicals could be developed to A survey made during the war showed that of 360,000,000 control specific pests. acres farmed in the United States about 45,000,000, or one The Food and Agriculture Organization of the United Nations eighth, are in crops which have been protected by chemicals. is now making world surveys on problems involving the use of Of the total crop value in 1943 (about 13 billion dollars) it was pesticides. Entomologists from 47 governments gathered in found that the value of the chemically protected crops was London recently to consider the loss of stored foodstuffs caused by insects and other types of pests which can be controlled by approximately 4.5 billion dollars, a little more than one third. Industry estimates indicate that when not only insecticides, but insecticides and fungicides. It was emphasized that the loss of fungicides, herbicides, rodenticides, soil and seed treatment stored food through infestation, in many cases, is higher than materials, defoliants, and plant hormones are included, the annual 10%. Even in countries with well-developed technical services value of agricultural chemicals consumed in the United States is the average is 5%. A later conference will be held by world scientists on another approximately $175,000,000 on a wholesale basis. Thus it is evident that chemical control is a very cheap form of crop insurance. phase of the food problem-the control of pests on growing crops. For years the importance of pest control has been pointed out However, a preliminary report has already been issued by the by citing crop losses. The importance of dollar savings should Food and Agriculture Organization on insecticides, fungicides, also be stressed. and allied products; this contains a survey of postwar conditions I n the years from 1936 to 1945, grasshoppers destroyed crops in nine specific areas of the world, and the present supply posivalued a t $400,000,000. During the same period control meastion and prospects for pesticides during 1948. ures saved crops worth $600,000,000, a t a cost of less than This organisation has also created a plant industry branch to $25,000,000. The story is the same on many other pests and on act as a world clearinghouse of information on plant industry many other products. problems and to encourage the use of insecticides and fungicides In addition to the actual savings in the production of food and in the lesser-developed countries of the world. fibers, chemicals have contributed tremendously to improved R E C ~ I V ~November D 22, 1947.
