Deposit structure effects on insecticide bioassays

Abstract

Agricultural application of pesticides is often done by atomization of the active ingredient and a carrier fluid. This atomized fluid lands on a plant surface and creates a mosaic of treated and untreated patches that we define as deposit structure. This structure influences the biological effect of the pesticide if dose per unit time is a factor in determining the overall toxicity of the pesticide. Laboratory bioassays are frequently carried out in such a way as to eliminate all effects of deposit structure. This bioassay methodology dictates the form of the observed dose-response relationship in these experiments. Although our observations do not invalidate previous bioassay methodology, they do suggest that current approaches provide a narrow view of dose-response relationships. These results affect bioassay methodology for testing toxicant efficacy and for experiments with insecticide resistance that use similar approaches to screen for resistance or study inheritance of pesticide resistance.