Abstract: Athetis dissimilis (Hampson) is a cryptic insect pest emerging as a serious agricultural pest in recent years. To explore effective and sustainable control of the pest, the pathogenicity of 5 isolates (YB8, TB1126, YB12, TB1349, YB15) of the entomopathogenic fungus Beauveria bassiana to 2^nd instar larvae of A. dissimilis was tested under laboratory condition to screen for high pathogenicity strains, and the colonization rate of YB8 in maize was measured. The isolates showed significant differences in pathogenicity to the A. dissimilis larvae, with median lethal times (LT₅₀) of 1.35, 2.16, 2.61, 1.68, and 2.16 d, respectively, and median lethal concentrations (LC₅₀) of 9.09×10⁷, 5.00×10⁸, 5.54×10⁹, 1.41×10¹¹, and 2.61×10¹² conidia/mL, respectively. At 26℃, conidial production of YB8 reached 1.094×10⁷, of which 89.66% germinated. When YB8 was applied at 1×10⁹ conidia/mL, the accumulative mortality of A. dissimilis 2^nd instars reached 100%, resulting in cadaver rate of 86.67% at 10 d post application. The colonization rate of YB8 was 44.44% in maize root, 51.59% in stem, and 36.30% in leaf. These results show that the strain YB8 is potential for further exploitation.

Key words: Athetis dissimilis, Beauveria bassiana, strain screening, endophytic