多杀霉素对小菜蛾和斜纹夜蛾的毒力及对小菜蛾的田间药效评价

Virulence of Spinosad against Plutella xylostella and Spodoptera litura and Field Efficacy Evaluation on P.xylostella

室内测定10%多杀霉素悬浮剂对小菜蛾和斜纹夜蛾的毒力,并进行多杀霉素防治小菜蛾的田间试验。结果表明,10%多杀霉素悬浮剂对小菜蛾3、4龄幼虫的LC50分别为1.9650、3.6756 mg/L,对斜纹夜蛾3、4、5、6龄幼虫的LC50分别为11.3105、229.7691、749.5139、4817.3030 mg/L;10%多杀霉素悬浮剂田间防治小菜蛾,18.75、22.5、26.25 g/hm^(2)剂量处理均对小菜蛾有明显的效果,药后1 d防治效果分别为21.08%、44.27%、71.32%,药后7 d防治效果分别为84.63%、92.38%、94.51%,经方差分析,药后3 d,22.5 g/hm^(2)处理与26.25、18.75 g/hm^(2)处理差异均达显著水平。多杀霉素对小菜蛾的毒力高于对斜纹夜蛾的毒力,因而可用于防治小菜蛾而不适于斜纹夜蛾的防治;田间使用10%多杀霉素悬浮剂防治小菜蛾适宜使用量为有效量22.5 g/hm^(2)。

Virulence of spinosad 10%suspension concentrate(SC)against Plutella xylostella and Spodoptera li⁃tura was determined in labor,and the control effect against P.xylostella was assayed in fields.Results showed that the LC50 value of spinosad against 3rd and 4th instar larva of P.xylostella is 1.9650 mg/L and 3.6756 mg/L.How⁃ever,for the 3rd,4th,5th,6th instar larva of S.litura,the value is 11.3105,229.7691,749.5139,4817.3030 mg/L,respectively.Spinosad 10%SC has a good filed control effect against P.xylostella when the application dos⁃age is 18.75,22.50,26.25 g/ha.The control effect of 1 d post-application is 21.08%,44.27%,71.32%,respectively.The control effect of 7 d post-application reached to 84.63%,92.38%,94.51%,respectively.Variance analysis showed that 3 d post-application,the control effect of 22.5 g/ha treatment is higher than 18.75 g/ha treatment,and lower than 26.25 g/ha treatment both at a 0.05 level.The toxicity of spinosad to P.xylostella is higher than S.litura,the reasonable application dosage is 22.5 g/ha.