INSECTICIDE TOXICITY IN EUROPEAN CORN-BORER (LEPIDOPTERA, PYRALIDAE) - OVICIDAL ACTIVITY AND RESIDUAL MORTALITY TO NEONATES

Field and laboratory studies were conducted using selected carbamate, organophosphate, and pyrethroid insecticides to quantify their toxicity to European corn borer, Ostrinia nubilalis (Hubner), eggs and residual mortality to neonates. Field studies included most insecticides currently registered for O. nubilalis on vegetable crops, as well as recently developed pyrethroids. Insecticides with the greatest ovicidal activity in field trials, in decreasing order, included methomyl, encapsulated methyl parathion, permethrin, thiodicarb, zeta-cypermethrin, and lambda-cyhalothrin. With the exception of methomyl, significant larval mortality was also observed for each material. Of all materials tested, only methomyl previously was assumed to have ovicidal activity on O. nubilalis. Laboratory bioassays were conducted to estimate the LC(50) for insecticides showing the greatest ovicidal activity in the field. Insecticides with the greatest ovicidal activity included, in decreasing order, zeta-cypermethrin, lambda-cyhalothrin, permethrin, methyl parathion, esfenvalerate, and methomyl. With the exception of methomyl, all insecticides demonstrated high levels of residual toxicity to neonates. Ovicidal activity of methomyl in the field but low inherent toxicity to eggs in the laboratory bioassay was partially explained by the use of a higher field rate relative to the pyrethroids. Results from this study will be useful for improving the timing of insecticide applications against O. nubilalis and necessary for refinement of an O. nubilalis management model.