THE DEVELOPMENT OF EQUIPMENT IN THE APPLICATION OF AGRICULTURAL 
CHEMICALS 
Walter M. Carleton, L. A. Liljedahl, Frank Irons, O. K. Hedden, and R. D, Brazee’ 
INTRODUCTION 
The effectiveness of any program to reduce chemical residues on plants and animals 
as well as the cost of applying those chemicals will be greatly affected by the kind of 
equipment used and the skill with which it is operated. This is true whether the applica- 
tion is from the air, by ground machines, or under the soil surface. 
The problem of applying pesticides, if such are to be used, is to place the minimum 
required amount of chemical where needed withthe least amount possible going elsewhere 
due to waste or drift. The application must be made with equipment which is both econom- 
ical and practical, For example, some special operations might be accomplished by 
hand or with hand tools, but the operation would not be practical enough to be used even 
in research, 
Much progress has been made in pesticide application equipment in the last 25 years, 
and the USDA agricultural engineers can rightfully claim a proper share of credit. 
However, the methods of applying dusts and sprays are still relatively costly and crude 
and we, in the pest control business, in order to assure control, have used the simple 
expedience of applying more of these pesticides than the minimum amount actually 
needed to control the pests. This has run up the cost and increased the residue hazards, 
According to estimates only 10 to 20 percent of the material applied as dust by 
commercial equipment is deposited on the plant surfaces in such a manner as to be 
effective. The older methods of shaking a sack of dust over the plant or cranking a 
knapsack duster, both commonly used on tobacco farms, are even less efficient. Little 
is known of the efficiency of deposition of sprays or fogs on both animals and plants. 
The efficiency of pesticide application is of considerable economic importance. The 
annual losses to agriculture resulting from disease, insects, and weeds have been 
estimated at more than $7,000,000,000, The annual cost of chemicals used for pest 
control is estimated at more than $500,000,000. Improved equipment giving a more 
accurate control of application rates and a more uniform application might well reduce 
the chemicals needed for a given application by 5 to 10 percent thus resulting in savings 
of $25,000,000 to $50,000,000 annually. Further, more accurately controlled and uniform 
application of chemicals for pest control would materially aid in solving the problem of 
excessive residues, 
OPTIMUM PEST CONTROL ---- ASSUMPTIONS 
@ The ideal solution to reduction of chemical residues is elimination of the need for 
chemicals. This may come about by biological methods such as the fantastically 
successful screwworm eradication campaign. This method seems to offer the ulti- 
mate in efficiency. Another method for further elimination of chemicals is the 
application of pathogens (virus, bacterial, and fungus diseases) to control insect 
pests. The possibilities of this method of control through the introduction of 
selective diseases without harming the plant stirs the imagination. Yet we know 
little of means for depositing the bacteria or the virus and fungus most effectively. 
1Assistant Director, Agricultural Engineering Research Division, ARS, USDA; Assistant to Acting Chief, and Agricultural En- 
gineers, respectively; Crop Production Engineering Research Branch, Agricultural Engineering Research Division, ARS, USDA, 
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