The Coverage Factor in the Application of Dusts

Abstract

Two probabilities are involved in the application of dusts in the field: (1) the probability of reaching the insects with any insecticide at all (coverage), and (2) the probability of killing the insect with the dose that hits it (dosage). These can be distinguished by properly-designed dosage-response expts. Conc. of toxicant in the dust affects the probability of killing the insect. Of the factors which might affect coverage, conc. of toxicant and amt. applied per acre were studied. Conc. affected coverage because variations in amt. of diluent affected the electrostatic charge developed in the process of applying the dust. Amt. per acre within the limits used (10-80 lb.) had little or no effect on coverage. In terms of efficiency, small amts. of higher conc. dusts were preferable to high amts. of low-conc. dusts. In reducing amt. used per acre, less control is lost if fewer lb. of dust are applied, rather than the same number of lb. of a lower conc.