关键词: 莱氏绿僵菌, 高效氯氰菊酯, 斜纹夜蛾, 亚致死剂量, 增效作用

Abstract: 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 LC₅₀ value of M.rileyi on the 5th instar S.litura larvae decreased from 8.22×10⁵conidia/mL to 2.06×10⁵conidia/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 1×10⁵ and 1×10⁶conidia/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 1×10⁸and 1×10⁹conidia/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.

Key words: Metarhizium rileyi, Beta-cypermethrin, Spodoptera litura, Sublethal dosage, Synergetic effect