Stuty on the cause of low toxicity of rotenone against Spodoptera litura and the synergistic effect of rotenone mixture
The objective of this study was to identify the underlying mechanism responsible for the low toxicity of the botanical insecticide rotenone against Spodoptera litura.Additionally,the synergistic effects of rotenone mixtures were investigated.For this purpose,the leaf dipping method was used to assess the biological activity of rotenone and rotenone mixtures on S.litura larvae.Meanwhile,the activities of three detoxification metabolic enzymes in S.litura were determined.The results showed that the LC50 of rotenone against the third-instar larvae was 1 081.41 μg/mL(72h),indicating a low level of toxicity to S.litura.The carboxylesterase in the midgut of S.litura was significantly affected by rotenone,with a maximum induction rate of 90.26％.It was hypothesized that the detoxification effect of the S.litura larvae to rotenone was related to this enzyme.The synergistic effect of rotenone in combination with cinnamon oil,fenzoylhydrazine,and Bacillus thuringiensis was also studied.The findings revealed that the insecticidal activities of the mixtures were significantly improved,and there was an enhanced inhibition of midgut detoxification enzymes in S.litura.
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