Abstract: 【Aim】 To explore the physiological and biochemical mechanism of the sublethal effect of chlorantraniliprole against Pleonomus canaliculatus, and to elucidate the effects of low lethal doses of chlorantraniliprole on food utilization, the contents of biochemical substances used as energy sources and the activities of digestive enzymes, protective enzymes and detoxification enzymes in P. canaliculatus larvae. 【Methods】 The toxicity of chlorantraniliprole against the 3rd instar larvae of P. canaliculatus was determined by soil mixed pesticide method in the laboratory. The effects of chlorantraniliprole at the LC₁₀, LC₂₅ and LC₄₀ doses on the nutritional indices and contents of biochemical substances used as energy sources in P. canaliculatus larvae were determined. The dynamic changes in the activities of digestive enzymes (protease, α-amylase, lipase and trehalase), protective enzymes (CAT, POD and SOD) and detoxifying enzymes (CarE, MFO and GST) in the 3rd instar larvae of P. canaliculatus at 1, 6, 12, 24, 48 and 72 h after exposure to chlorantraniliprole were detected by enzyme kinetic method. 【Results】 Chlorantraniliprole had higher toxicity to the 3rd instar larvae of P. canaliculatus, with the LC₅₀ value of 1.2397 mg/kg. The mean relative growth rate (MRGR) and approximate digestibility (AD) were significantly decreased when the 3rd instar larvae of P. canaliculatus were exposed to LC₂₅ and LC₄₀ of chlorantraniliprole, leading to serious disturbance of their food utilization. Chlorantraniliprole at LC₁₀, LC₂₅ and LC₄₀ doses significantly decreased the contents of protein, lipid, carbohydrate and trehalose, and the activities of protease, α-amylase, lipase and trehalose, significantly increased the activities of detoxifying enzymes (CarE, MFO and GST) and protective enzymes (CAT, POD and SOD) in the 3rd instar larvae of P. canaliculatus treated with these doses of chlorantraniliprole, and caused the delayed growth and development of the treated larvae. 【Conclusion】 Chlorantraniliprole has high insecticidal activity against P. canaliculatus larvae. In P. canaliculatus larvae exposed to low lethal doses of chlorantraniliprole, the activities of digestive enzymes are inhibited, resulting in the reduction of food utilization and delaying the growth and development of P. canaliculatus, and the activities of detoxifying and protective enzymes are induced, preventing the invasion of external toxicants. These results provide a theoretical basis for elucidating the mechanisms of sublethal effect and action of chlorantraniliprole against P. canaliculatus.

Key words:  Pleonomus canaliculatus; chlorantraniliprole, toxicity, sublethal effects, digestive enzyme, protective enzyme, detoxifying enzyme, enzyme activity