Residual and Topical Toxicity of Various Insecticides to the Lesser Mealworm (Coleoptera: Tenebrionidae)

Abstract

Experiments were conducted to determine the relative toxicities of seven insecticides to adult and late instar lesser mealworms and to compare the residual activity of permethrin and carbaryl on polystyrene and unpainted plywood. In the residual activity tests, insecticide performance was altered by differences in formulation, surface type, and life stage of the insect. Wettable powder formulations were more effective on polystyrene than were emulsifiable concentrate formulations. Residual activity of permethrin and carbaryl was longer and more effective on polystyrene surfaces than on unpainted plywood. Tetrachlorvinphos WP (0.50% AI) gave excellent control on both surfaces. In the topical application experiments, permethrin, famphur, and tetrachlorvinphos were most toxic. Dimethoate, tetrachlorvinphos, carbaryl, and propoxur were more toxic to late instars than to adults. The reverse was true for malathion. Protection administered to polystyrene insulation by surface sprays may be nullified by the burrowing habits of the insect. Toxicity profiles of different mealworm populations may depend on different spray regimes within poultry houses.