July 1942 y^-^^-^v E-574 'SSSS'-f^ EQUIPMENT AVAILABLE FOR APPLYING CONCENTRATED SPRAYS By S. F. Potts, Division of Forest Insect Investigations The demand for methods of insecticidal control which save labor and materials has been accentuated by the war emergency. Conventional dusting methods often result in wastage of materials and poor adherence of the in- secticide. Conventional spraying with dilute sprays is labor-consuming and often requires heavy, expensive, high-pressure equipment. The application of insecticides and fungicides in the form of concentrated sprays saves labor, time, and materials. At present this method is restricted because there is very little efficient equipment on the market designed specifically for applying concentrates. Consequently the available equipment adaptable for this purpose is not only limited, but it is not nearly so efficient as are machines which may be developed and improved specifically for this pur- pose at some later date. This paper is intended to indicate the equipment which can be purchased or assembled at the present time, seme of its advan- tages and disadvantages, and the insecticidal mixtures and concentrations which are best suited for use in such equipment. Concentrated sprays (excepting high-viscosity oils) are nearly as fluid as water. Their insecticidal concentration is many times that of dilute sprays. For example, a common lead arsenate concentrate contains 40 percent oi lead arsenate as compared with 0.5 percent of lead arsenate in dilute spray containing 4.2 pounds of insecticide per 100 gallons (838 pounds) of mixture. Methods for preparing concentrated spray mixtures are discussed in other papers. 1_/ Concentrated sprays may be applied at any time to either 1/ Potts, S. F. 1939. Concentrated Mixtures for Aerial Spraying. Jour. Econ. Ent. 32 (4): 576-580. Potts, S. F. 1940. Concentrated Spray Mixtures and Their Application by Ground and Aerial Equipment as Compared with Standard Spraying and Dusting Methods. Bur. Ent. and PI. Quar. E-508, pro- cessed. - 2 wet or dry foliage, as the spray does not drip or run off the leaves. They adhere better than dilute sprays or dusts. This makes possible the applica- tion of less insecticide and fewer treatments. Areas may be covered many times more quickly with concentrated than with dilute spray. In general, fine atomization makes possible the use of a small quantity of spray per acre, and this necessitates the use of a high concentration of the insecti- cide. It is, therefore, not practical to apply coarsely atomized concen- trates. For given pressures, atomization increases as the rate of output of spray mixture per aperture decreases. A difficulty with most equipment is that it applies too much coarsely atomized concentrated spray per acre. This makes necessary the use of lower concentrations, higher quantity rates, greater insecticidal dilution, higher pressures, and higher pump capacities. In order to obtain good coverage without using too much insecticide, concen- trates should be applied as though they were dust materials rather than sprays . As compared with water-borne sprays, undiluted oils are more finely atomized, spread much better, evaporate less rapidly, and flow through nozzle orifices at a slower rate, but are more expensive, and are less safe on tender foliage. Concentrated sprays may be applied with a type of hand-pump atomizer, or with knapsack and power sprayers equipped with special nozzles. Hand Atomizer The type of hand atomizer best suited for applying concentrates is shown in figure 1. This type is far superior to the so-called continuous-pressure atomizers because (1) the orifice of the tube which conducts the liquid from the spray container to the outside ranges from 0.1 to 0.15 inch in diameter, which is large enough to prevent clogging, and (2) it discharges the liquid at a slower rate, which permits it to be more finely atcmized. The use of the hand atomizer is limited to yards, gardens, and small fields of plants or trees that are not over 6 feet in height. When the plants are 2 feet high or less, the operator is likely to become tired quickly unless an ex- tension rod of 12 to 30 inches in length is used. It is often difficult to cover the underside of leaves well with insecticide applied by existing types of hand atomizers, since they are not provided with a means of directing the spray at an angle. The degree of atomization provided by hand atomizers is not sufficient- ly fine to give as good kill of certain small sucking insects when applying concentrates as when applying dilute sprays. In order to obtain a kill as good as or better than that obtained by dilute sprays, it would be necessary for the concentrated spray droplets to be approximately one-fifth as large as those provided by the present equipment when oil is used as the in- secticidal carrier, or approximately one-tenth as large if water is the car- rier. Atomization by existing hand equipment is sufficiently fine to control effectively all sizes of chewing insects when the mixture does not contain more than 2.5 pounds of powdered insecticide per gallon of water. At a 3 - concentration of 2 pounds of insecticide per gallon of mixture, 5 gallons would be required to give 10 pounds of insecticide per acre. Fungicides or combina- tion insecticides can be added to the mixture. For example, a mixture con- taining 1.5 pounds of lead arsenate or cryolite, 1 pound of sulfur, and 1 pound of copper oxide per gallon has been applied. Knapsack Sprayers The use of knapsack equipment is limited by the rate of delivery and degree of efficiency of the atomizing nozzles. Most nozzles deliver too much mixture (gallons per hour) and do not atomize it sufficiently. How- ever, tv/o types of nozzles 2/ atomized concentrates well enough at low pres- sures to be used for controlling many chewing insects, including the gross feeders that consume the whole or parts of leaves. The nozzle has an aper- ture of 0.025 inch and delivers 5.04 gallons of water per hour at 75 pounds pressure, as compared with 33.6 gallons for ordinary one-sixteenth inch aperture nozzles. When spraying truck crops the operator should move fasc enough to cover an acre with 8 to 10 gallons of mixture. Well-stocked ccnifercus plantations require 12 to 15 gallons per acre. These are average •3s which may be varied to meet specific conditions. Usually it is more practical to use a single nozzle, except in cases where effective control ca:. be obtained by using a broom of two or three nozzles (fig. 2) spaced 15 to 18 inches apart. Power Equipment The nozzle just described for the knapsack sprayer can be attached to the broom, row boom, or broadcast boom of power sprayers. The equipment preferably should not be powerful or heavy. A -^-horsepower engine and a pump capable of delivering 100 gallons of mixture per hour are adequate for a 6-row boom, since only about 4 to 7 gallons will be applied per nozzle per hour at a pressure of 100 pounds or less. There should be a suitable strainer in the spray line but none in the nozzle. A small increase or de- crease in size of nozzle orifice makes a big difference in gallons delivered, but a small increase or decrease in pressure does not greatly increase or decrease spray output. It is necessary to quadruple the pressure in order to double the output. Increasing the pressure causes seme increase in atomization. Decreasing the size of the nozzle orifice also increases atomi- 2/ Nozzle, number IS is made by the Spray Engineering Company of 114 Central Street, Somerville, Mass. Its screen should be removed when concentrates are to be applied. The IS nozzle is capable of applying all insecticides dissolved in water or oil, such as nicotine solution, pyrethrum extract, and derris extract, and suspensions of fine insecticide particles such as copper oxide, lead arsenate, calcium arsenate, cryolite, etc., af- ter these suspensions have been strained through a 40- or 50-mesh screen. Another promising nozzle (number T68037) made by the same company delivers slightly less spray per hour, and has an orifice 2.2 times as large which might reduce clogging. Only laboratory tests have been made with it. zation. Nozzles with orifices as small as 0.018 inch in diameter can be used when light oils and insecticides dissolved in water are being applied, but they will clog when solid particles in suspension are being applied. There is less abrasion at the nozzle orifices if this part of the nozzle is made of hardened or stainless steel instead of brass. A 4-row sprayer with two IS nozzles per row will deliver 40.3 gallons of spray per hour at 75 pounds' pressure and cover 5.82 acres at 6.93 gal- lons per acre when traveling 4 miles per hour. 3/ The quantity of insecti- cide per gallon of mixture should vary with the number of gallons applied per acre. In general, the power machines are limited to controlling the same kinds of insects mentioned in connection with the knapsack sprayer, but there are seme exceptions. For example, Glasgow 4/ has used a power atom- izer equipped with a special type of conventional nozzle to control the pea aphid, using either rotenone extract or nicotine solutions in both water and oil. This machine traveled 5 miles per hour and usually had a long canvas trailer attached to it to increase the kill by fumigation when spraying with with nicotine mixtures. Sprayer units with a gasoline engine of 5 horsepower capacity or greater and capable of delivering as much as 200 pounds pressure can be converted for applying concentrates to trees up to 25 feet in height. This is done by providing a high-velocity blower and blower tube, such as are used on orchard dusters, and placing from one to five of the atomizing nozzles just described at the end of the blower tube. The strong blast of air serves to drive the spray into the trees. One gasoline engine drives both the sprayer and the blower. This method can also be used for broadcast spraying of crops. Aerial Equipment Aerial equipment now available consists almost entirely of airplanes equipped with air-driven rotary or centrifugal devices for dispersing atom- ized spray. 5/ This type of device is satisfactory for many purposes. For some purposes it is not entirely satisfactory since it tends to throw part 3/ To calculate the number of gallons that will be delivered per acre, multiply the rate of travel (m. p. h.) of the sprayer by the width (in feet) of strip or swath covered, and divide by 43,560 to obtain the acreage cov- ered. Then multiply the number of nozzles by the number of gallons delivered per nozzle per hour, and divide this product by the acreage covered. 4/ Glasgow, Hugh. 1942. The Use of Concentrated Sprays for Pea Aphid Control. N. Y. (Geneva) Agr. Expt. Sta. Dull. No. 698, pp. 12 to 14. 5/ A centrifugal device is shown in the following paper: Whitten, R. R., S. F. Potts, and E. H. Francis, 1941. Concentrated Spray Applied with an Autogiro for Control of Cankerworms. Jour. Econ. Ent. 34 (5): 692-696. of the mixture up en the aircraft, and it does not always cause sufficiently fine atomization for best control of such insects as aphids. Ground and preliminary aerial tests indicate that ether types of apparatus which utilize the principle of pressure or air atomization and which will be lighter, simpler, and more efficient than centrifugal devices can be made to oper- ate in the "slip stream". As compared with airplanes, autogiros are able to fly at much lower speeds, tern in smaller areas, and land on and take off from much smaller fields, and ere safer to operate. Thus far helicopters have not been tried for applying insecticides. It is believed that in the future the new types of autogiros and helicopters now being developed will play an important role in insect and disease control. Companies Making One or More Types of Concentrated Spray Atomizers Ground machines: John Bean Manufacturing Company, Lansing, Mich. Root Manufacturing Company, 1311 West 50th Street, Cleveland, Ohio. H. D. Hudson Manufacturing Company, 589 E. Illinois Street, Chicago, 111. Shell Oil Company, Inc., Technical Products Department, 50 W. 50th Street, New York City, N. Y. Electric Sprayit Company, Sheboygan, Wis. Essick Machinery Company, 1928 Santa Fe Avenue, Los Angeles, Calif. Breuer Electric Manufacturing Company, 5100 Ravenwood Avenue, Chicago, 111. Aerial atomizing apparatus: Hawke Crop Dusting and Spraying Company, Modesto, Calif. Independent Crop Dusting Company, San Francisco, Calif. Wilson Aerial Spraying Service, Seabrook Farms, Bridgeton, N. J. Companies Making Autogiros and Helicopters Autogiros: Pitcairn-Larson Autogiro Corporation, Willow Grove, Pa. Kellett Autogiro Corporation, Willow Grove, Pa. Helicopters: Vought-Sikorsky Aircraft, Stratford, Conn. Platt-LePage Aircraft Company, Eddystone, Pa. The United States Department of Agriculture does not guarantee or en- dorse the firms listed above or the reliability of their products. In fur- nishing this list no claim is made that it is complete and no discrimination is intended against any manufacturers not included. UNITED STATES DEPARTMENT OF AGRICULTURE PENALTY FOR PRIVATE USE TO AVOID OFFICE OF THE SECRETARY PAYMENT OF POSTAGE. $300 WASHINGTON, D. C. OFFICIAL BUSINESS Figure 1. — The type of hand atomizer found to be useful for applying concentrated sprays. Digitized by the Internet Archive in 2013 http://archive.org/details/equipmentavailabOOunit Figure 2. — A hand-operated compressed-air type of knapsack sprayer equipped with a l/^-inch (diameter) extension rod and a broom with three IS nozzles.' UNITED STATES DEPARTMENT OF AGRICULTURE OFFICE OF THE SECRETARY WASHINGTON, D. C. 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