Esterase Activity in Homogenates of Spodoptera frugiperda (J.E. Smith) Exposed to Low-Lethal Doses of Chlorantraniliprole and Emamectin Benzoate

Chlorantraniliprole and emamectin benzoate have been widely used to control pests including FAW. For effective pest control, the sublethal effects of these insecticides should be considered. The toxicity of chlorantraniliprole and emamectin benzoate to third-instar FAW larvae has been determined using topical application. Alpha esterase (EST-α) and beta esterase (EST-β) activity were also assessed after 1, 6, 12, 24, and 48 h of exposure of larvae to low doses of these insecticides. The susceptibility of FAW larvae to chlorantraniliprole and emamectin benzoate increased after 48 h, and the LD50 was 0.18 and 0.23 μg/larvae, respectively.EST-α and -β activity changed significantly in FAW larvae over time after exposure to insecticides. After only 1 h, EST-α, and -β activity after exposure of larvae to insecticides at LD10 showed no significant difference compared to control. However, under LD30 treatments, the activity of EST-α and -β decreased significantly. Significant reduction of EST-α and -β activity was observed in larvae after 48 h exposure to chlorantraniliprole at LD30 (0.5 and 0.15 nmol/min/mg protein, respectively) followed by emamectin benzoate (1.19 and 0.29 nmol/min/mg protein, respectively) compared with control activity. Sublethal doses of chlorantraniliprole and emamectin benzoate affected activities of EST-α and -β of FAW.