双委夜蛾高致病力球孢白僵菌的筛选及在玉米内定殖率的测定

双委夜蛾Athetis dissimilis（Hampson）为近年新发生的农业害虫，具有隐蔽为害的习性。为探索有效可持续的防治方法，实验室内测定了YB8、TB1126、YB12、TB1349和YB15共5株球孢白僵菌菌株对双委夜蛾2龄幼虫的致病力，筛选出高致病力白僵菌菌株，并测定其在玉米植株中的定殖率。结果表明：不同菌株对双委夜蛾的致病力存在较大的差异，LT₅₀分别为1.35、2.16、2.61、1.68和2.16 d，LC₅₀分别为9.09×10⁷、5.00×10⁸、5.54×10⁹、1.41×10¹¹和2.61×10¹²孢子/mL。菌株YB8在26℃下，产孢量1.094×10⁷个/mL，孢子萌发率89.66%，1×10⁹孢子/mL 10 d时双委夜蛾2龄幼虫死亡率达到100%，感染僵死率达到86.67%，在玉米根中定殖率为44.44%，茎中定殖率为51.59%，叶片中定殖率为36.30%。具有较大的开发潜力。

Screening of High Pathogenicity Strains of Beauveria bassiana against Athetis dissimilis and Detection of Colonization Rate in Maize

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.