Abstract: 【Aim】To evaluate the virulence of biocontrol fungi isolated from vegetable gardens and the toxicity of commonly used insecticides against Megalurothrips usitatus. 【Methods】 Three insect pathogenic fungi isolated from pest samples in vegetable gardens were identified via morphology and ITS sequence analysis. The virulence of the three fungal species (1×10⁵-1×10⁹ cfu/mL) against M. usitatus adults was assessed after infection for 4-9 d. The toxicity of five commonly used insecticides including spinetoram (0.05, 0.1, 0.2, 0.4, 0.8 and 1.6 mg/L), spinosad (0.125, 0.25, 0.5, 1, 2 and 4 mg/L), emamectin benzoate (40, 80, 160, 320, 640 and 1 280 mg/L), thiamethoxam (20, 40, 80, 160, 320 and 640 mg/L) and cyantraniliprole (50, 100, 200, 400, 800 and 1 600 mg/L) against M. usitatus adults at 48 h post-treatment was determined using leaf-tube insecticide film method. 【Results】Three biocontrol fungi Metarhizium anisopliae Ma-g07, Beauveria bassiana Bb-g06 and Akanthomyces attenuatus La-sl04 were isolated and identified. The corrected mortality rates of adult M. usitatus at 9 d after infection by M. anisopliae Ma-g07, B. bassiana Bb-g06 and A. attenuatus La-sl04 at the concentration of 1×10⁹ cfu/mL were 100%, 91.38% and 62.50%, respectively, and the median lethal time (LT₅₀) values of M. anisopliae Ma-g07, B. bassiana Bb-g06 and A. attenuatus La-sl04 at the concentration of 1×10⁹ cfu/mL against M. usitatus adults were 4.39, 5.15 and 6.09 d, respectively. The median lethal concentration (LC₅₀) values of M. anisopliae Ma-g07 against adult M. usitatus at 5－9 d after infection were 1.79×10⁸, 2.99×10⁷, 3.30×10⁶, 1.06×10⁶ and 9.58×10⁵ cfu/mL, respectively, those of B. bassiana Bb-g06 were 7.46×10⁸, 7.79×10⁷, 5.01×10⁶, 6.09×10⁵ and 1.63×10⁵ cfu/mL, respectively, and those of A. attenuatus La-sl04 were 7.01×10⁹, 1.11×10⁹, 4.96×10⁸, 3.51×10⁸ and 2.80×10⁸ cfu/mL, respectively. The LC₅₀ values of spinetoram and spinosad against M. usitatus adults at 48 h after treatment were 0.35 and 0.95 mg/L, respectively, which were much lower than those of emamectin benzoate, thiamethoxam and cyantraniliprole (154.55, 297.88 and 315.14 mg/L, respectively). 【Conclusion】M. anisopliae Ma-g07 and B. bassiana Bb-g06 exhibit high pathogenicity and biocontrol potential against M. usitatus. Spinetoram and spinosad have higher toxicity  to M. usitatus adults among the five insecticides. It is suggested that in the future, the research on the combined application of these two biocontrol agents and two insecticides should be carried out for controlling M. usitatus. This study provides a basis for screening biocontrol resources and guidance for the rational selection of insecticides for M. usitatus and the combined application of biocontrol fungi and insecticides.

Key words: Megalurothrips usitatus, Metarhizium anisopliae, Beauveria bassiana; Akanthomyces attenuatus, insecticides