Direct, Indirect, and Residual Toxicities of Insecticide Sprays to Western Spruce Budworm,choristoneura Occidentalis(lepidoptera: Tortricidae)

The toxicities of acephate, aminocarb, carbaryl, chlorpyrifos, chlorpyrifos-methyl, methomyl, mexacarbate, permethrin, and trichlorfon to last instar western spruce budworm,Choristoneura occidentalisFreeman, were significantly altered by the presence of host-plant foliage. The pyrethroid permethrin was significantly more toxic when sprayed directly on fully exposed larvae than when first sprayed on foliage. However, all other toxicants were more toxic sprayed on foliage. A toxicologically-based method was used to assess the residual toxicities of the nine chemicals. Each chemical was applied to potted seedlings at its respective LD90-foliage, then weathered for up to 7 days. Significant differences in toxicity were related to both insecticide and weathering interval. The toxicities of carbaryl and permethrin were least affected by weathering.