Response comparison of protective and detoxification enzymes in Spodoptera frugiperda(J. E. Smith) and Spodoptera litura(Fabricius) larvae to two insecticides

【Objective】The research aimed to clarify the response of different insecticides on the activities of protective enzymes and detoxification enzymes in the larvae of Spodoptera frugiperda(J. E. Smith) and Spodoptera litura(Fabricius) to two insecticides, and to provide theoretical basis for further study on the field control and and insecticide resistance mechanism of S. frugiperda and S. litura.【Method】The toxicity of emamectin and chlorantraniliprole to the 3^rd instar larvae of S. frugiperda and S. litura were assayed by leaf-dipping method by feeding wheat leaves treated with sublethal concentration(LC₂₅) and median lethal concentration(LC₅₀) of the pesticides respectively, and the activities of protective enzymessuperoxide dismutase(SOD), peroxidase(POD) and catalase(CAT)and detoxification enzymesglutathione S-transferase(GST), cytochrome P450(CYP450) and carboxylesterase(CarE)in larvae after being treated for 6, 12, 18, 24 and 48 h were measured and analyzed.【Result】The toxicity of emamectin to S. frugiperda and S. litura was higher than that of chlorantraniliprole. The activity of CYP450 in both pests increased after the two insecticide treatments, and was significantly higher in S. frugiperda than that in S. litura. The CYP450 activity in S. frugiperda was more active at low concentration(LC₂₅) of emamectin and chlorantraniliprole than at high concentration(LC₅₀), which was the highest at 48 h as 15.72±0.41(emamectin) and 15.36±0.47 ng/mL(cholrantraniliprole). However, the activities of two detoxification enzymes GST and CarE in S. frugiperda were lower than those in S. litura after emamectin treatment. The activities of protective enzymes SOD and POD in both pests decreased after treated with emamectin, and were lower in S. frugiperda than those in S. litura;while the activities of SOD and POD in S. frugiperda increased after treated with chlorantraniliprole. The activities of SOD and CAT were higher in both pests at LC₅₀ chlorantraniliprole than at LC₂₅, and were higher in S. frugiperda than in S. litura. The response activities of protective enzymes and detoxification enzymes in both pests were greatly affected by the two insecticides, and species, insecticide, concentration, time, species×concentration and insecticide×concentration had extremely significant effects on the activities of protective enzymes and detoxification enzymes(P<0.01). There was a strong correlation between the activities of SOD and CAT of both S. frugiperda and S. litura under two insecticides treatments.【Conclusion】The susceptibility of S. frugiperda to emamectinis higher than that of S. litura, while the sensitivity to chlorantraniliprole is lower than that of S. litura, and the two pests enhance detoxification metabolism of insecticides by increasing CYP450 activity. In agricultural production, it is recommended to use emamectin as an agent for controlling S. frugiperda.