Deposit structure effects on insecticide bioassays

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 defi ne 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 bioas say methodology dictates the form of the observed dose-response relationshi p in these experiments. Although our observations do not invalidate previou s bioassay methodology, they do suggest that current approaches provide a n arrow view of dose-response relationships. These results affect bioassay me thodology for testing toxicant efficacy and for experiments with insecticid e resistance that use similar approaches to screen for resistance or study inheritance of pesticide resistance.