亚致死剂量高效氯氰菊酯对莱氏绿僵菌的增效作用

Synergetic Effects of Sublethal Dosage of Beta-cypermethrin on Metarhizium rileyi against Spodoptera litura

为了提高莱氏绿僵菌(Metarhizium rileyi)对斜纹夜蛾的致死效果,采用浸渍法测定了亚致死剂量高效氯氰菊酯对莱氏绿僵菌的增效作用。结果表明,添加0.5 mg/L高效氯氰菊酯后,M.rileyi对5龄斜纹夜蛾幼虫的孢子致死中浓度(LC_(50))由8.22×10^(5)个/mL降至2.06×10^(5)个/mL,致死中时(LT50)也有不同程度缩短。对180 h的累计死亡率进行方差分析,M.rileyi+0.5 mg/L高效氯氰菊酯处理在孢子浓度1×10^(5)、1×10^(6)个/mL时,对斜纹夜蛾的致死效果分别为56.86%和75.93%,明显高于单独使用M.rileyi处理的效果(26.67%和53.33%);孢子浓度提高到1×10^(8)、1×10^(9)个/mL时,高效氯氰菊酯+M.rileyi与单独使用M.rileyi的效果差异不显著。高效氯氰菊酯亚致死剂量(0.5 mg/L)对M.rileyi孢子萌发和菌丝生长无抑制作用。可见,亚致死剂量高效氯氰菊酯对低剂量M.rileyi有明显的增效作用,对高剂量M.rileyi增效不明显。

To improve the lethal effect of Metarhizium rileyi on Spodoptera litura,the synergistic effect of sublethal dosage of beta-cypermethrin on M.rileyi was determined by dipping method.The results showed that,combined with 0.5 mg/L beta-cypermethrin,the LC_(50)value of M.rileyi on the 5th instar S.litura larvae decreased from 8.22×10^(5) conidia/mL to 2.06×10^(5) conidia/mL,meanwhile,the LT50 value was also shortened.The analysis of variance on the cumulative mortality of 180 h indicated that,with the presence of 0.5 mg/L beta-cypermethrin,the lethal effects of M.rileyi at the concentration of 1×10^(5) and 1×10^(6) conidia/mL on S.litura were 56.86%and 75.93%respectively,which were significantly higher than the effects of M.rileyi alone(26.67%and 53.33%).However,as the spore concentration was increased to 1×10^(8) and 1×10^(9) conidia/mL,no significant difference was found between the effects of beta-cypermethrin+M.rileyi and M.rileyi alone.The sublethal dose of beta-cypermethrin(0.5 mg/L)had no inhibitory effect on the spore germination and mycelial growth of M.rileyi.It can be concluded that sublethal dosage of beta-cypermethrin has significant synergistic effect on M.rileyi at low conidial concentrations,but not at high concentrations.