Exposure to insecticides cause mortality, respiratory disturbs, and antifeeding effects in Anticarsia gemmatalis

The velvetbean caterpillar (VBC), Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae), is a significant soybean pest in the Americas and controlled mainly with chemical insecticides. Toxicity, survival, respiration, and anti-feeding effect of the VBC larvae exposed to four neurotoxic insecticides (α-cypermethrin, abamectin, chlorpyrifos, and thiamethoxam) by ingestion were evaluated. Toxicity bioassays demonstrated that abamectin (LC₅₀ = 0.097 g L^–1), thiamethoxam (LC₅₀ = 0.537 g L^–1), and chlorpyrifos (LC₅₀ = 1.998 g L^–1) were toxics to VBC. The survival rate was 98% in control caterpillars, declining to 35% in larvae exposed to LC₅₀ of thiamethoxam, 26% in larvae treated with chlorpyrifos, 23% in larvae treated with abamectin, and 10% in those treated with α-cypermethrin. The neurotoxic insecticides reduced low respiration rates and produced feeding inhibition in VBC caterpillars. Our results suggest that abamectin, α-cypermethrin, chlorpyrifos, and thiamethoxam are highly effective against VBC and may be implemented to manage its populations in soybean crops.