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 toxicit y to European corn borer, Ostrinia nubilalis (Hubner), eggs and residu al mortality to neonates. Field studies included most insecticides cur rently registered for O. nubilalis on vegetable crops, as well as rece ntly developed pyrethroids. Insecticides with the greatest ovicidal ac tivity in field trials, in decreasing order, included methomyl, encaps ulated methyl parathion, permethrin, thiodicarb, zeta-cypermethrin, an d lambda-cyhalothrin. With the exception of methomyl, significant larv al mortality was also observed for each material. Of all materials tes ted, 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 fie ld. Insecticides with the greatest ovicidal activity included, in decr easing order, zeta-cypermethrin, lambda-cyhalothrin, permethrin, methy l parathion, esfenvalerate, and methomyl. With the exception of methom yl, 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 f rom 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.