应用叶片保护率评价阿维菌素对小菜蛾的毒力

研究目的】尝试采用叶片保护率评价阿维菌素对小菜蛾（Plutella xylostella (Linnaeus)）2龄、3龄幼虫的毒力，以期为该药毒力的准确评价提供资料。【研究方法】浸叶法测定阿维菌素对小菜蛾2龄、3龄幼虫室内毒力的同时，观察记录24h、48h、72h校正死亡率、叶片保护率【结果】对小菜蛾2龄幼虫，24h、48h、72h的LC50分别为>10.00mg/L、2.87mg/L、0.56mg/L；相同时间内PC50分别为0.25 mg/L、0.82mg/L、1.43mg/L。对3龄幼虫，24h、48h、72h的LC50分别为>10.00mg/L、6.20mg/L、3.00mg/L；相同时间内PC50分别为<0.16mg/L、0.04mg/L、4.25mg/L。【结论】根据叶片保护率，可以发现阿维菌素对小菜蛾影响快，但是当阿维菌素毒力达到稳定时，必须有较高的校正死亡率，否则达不到理想的叶面保护效果。

Toxicity assessment of avermectin on diamondback moth, Plutella xylostella (Linnaeus), by means of leaf protection rate

Objective] To provide data for toxicity assessment of avermectin on diamond back moth, Plutella xylostella (Linnaeus), the leaf protection role of avermectin was studied. Method] The toxicity was tested by leaf-dipping method and the corrected mortality and leaf protection rate at 24h、48h or 72h were calculated.Results] For the 2nd instar larvae, the LC50s at 24h、48h and 72h were >10.00mg/L、2.87mg/L and 0.56mg/L, respectively. The PC50s at the respective duration were 0.25 mg/L、0.82mg/L and 1.43mg/L, respectively. Meanwhile, for the 3rd instar larvae, the LC50s at 24h、48h and 72h were >10.00mg/L、6.20mg/L and 3.00mg/L, respectively. The PC50s at the respective duration were 0.25 mg/L、0.82mg/L and1.43mg/L, respectively. Conclusion] Based on the leaf protection rate, the effect of avermectin on the tested insects came out quickly after tratment. But the corrected mortality should reach a high level while the toxicity became stable, otherwise the leaf protection effect would not be well enough.