Topical and residual toxicity of six pesticides to Orius majusculus

Abstract

The toxicity of six pesticides (four insecticides and two fungicides) to Orius majusculus (Reuter) (Hemiptera: Anthocoridae) adults and nymphs was determined using different exposure methods. Mortality upon topical exposure to abamectin, endosulfan and spinosad at recommended field doses ranged from 56% to 100% after 24 h. However, in leaf residue tests, toxicity to both life stages decreased significantly, ranging from 0% to 33% mortality. Benomyl and copper salts + mancozeb (fungicides) were much less toxic to O. majusculus, with less than 15% mortality of either adults or nymphs in topical and residue bioassays. In persistent toxicity tests, insects were exposed to the same three insecticides for 4 days; mortality varied from 38% to 100%. Egg hatching was not significantly affected when abamectin, endosulfan and spinosad were topically applied. Number of eggs laid per female in choice and no-choice tests did not differ significantly from the control. The insecticides did not show considerable repellent effect in the choice tests. Topical, residue and systemic uptake methods were also compared to determine the differences in the toxicity levels of imidacloprid, a systemic insecticide. However, 100% mortality occurred with all methods.