Abstract:
【Aim】 The diamondback moth (DBM), Plutella xylostella (L.), is one of the most important pests of cruciferous plants in the world. Cyantraniliprole is a novel anthranilic diamide insecticide registered for the control of lepidopteran pests, but there is sparse information available regarding its effects on P. xylostella. Here, we studied the effects of cyantraniliprole on biological characteristics and the related enzyme activities of P. xylostella. 【Methods】 The leaf-dipping method was used to test the toxicity of cyantraniliprole to the 3rd instar larvae of P. xylostella, and the LC₂₀ and LC₅₀ values were determined. The 3rd instar larvae were transferred onto cabbage leaves soaked in LC₂₀ and LC₅₀ of cyantraniliprole solution ［20% lethal concentration (LC₂₀)=0.03 mg/L and 50% lethal concentration (LC₅₀)=0.08 mg/L］ and allowed to feed for 48 h, then the biological characteristics such as the pupal duration, pupation rate, adult emergence rate and so on were recorded, and the related enzyme activities were also measured. 【Results】 The results showed that the estimated LC₂₀ and LC₅₀ values of cyantraniliprole on the 3rd instar larvae in leaf dip bioassay were 0.03 mg/L and 0.08 mg/L, respectively. Cyantraniliprole at LC₂₀ and LC₅₀ concentrations (LC₂₀=0.03 mg/L, LC₅₀=0.08 mg/L) could extend the duration of the 4th instar and pupal stage, and reduce the pupal weight and fecundity of P. xylostella. In treated groups, the pupation rate (F=42.19; df=2,6; P<0.05) and adult emergence rate (F=13.15; df=2,6; P=0.006) were significantly lower than those in the control group, respectively. Cyantraniliprole exposure also significantly increased the activities of protective enzymes (CAT and POD) at 12 h after treatment, but caused no effect on the activities of detoxification enzymes (CarE: P=0.43; GST: P=0.54; ODM: P=0.25). In contrast, cyantraniliprole exposure increased the activities of detoxification enzymes at 48 h after treatment, but caused no effect on the activities of protective enzymes (CAT: P=0.58; POD: P=0.13). 【Conclusion】 The LC₂₀ and LC₅₀ concentrations of cyantraniliprole have negative effects on the growth and development of P. xylostella, which could reduce the population density of the next generation. Moreover, cyantraniliprole at these two concentrations could induce the activities of the related detoxifying enzymes of P. xylostella. This finding is of great significance in guiding the use of this insecticide in field and delaying the development of insecticide resistance.

Key words: Plutella xylostella, cyantraniliprole, toxicity, enzyme activity, biological characteristics