Persistence and activity of mexacarbate and its metabolites against spruce budworm larvae

This study was conducted to determine if metabolites of mexacarbate contribute to its residual toxicity to spruce budworm (Choristoneura fumiferana) larvae. Potted white spruce (Picea glauca) trees were treated with ‘Zectran’ UCZF # 19 at 100 g a.i. ha−1 and kept in a glasshouse. Mexacarbate residues declined by 98–99% within three days and reached non‐detectable levels 10 days after treatment. Mortality of larvae fed on buds from these trees declined more gradually and was still 19–27% when exposed 10 days after treatment. The very low levels of mexacarbate (