Screening of Beauveria bassiana with High Pathogenicity to Agrotis ipsilon in Tobacco Fields

To screen for Beauveria bassiana strains with high pathogenicity to Agrotis ipsilon, a comprehensive evaluation was carried out on the pathogenicity of nine B. bassiana strains using multiple factors including fungal growth rate, conidial production, germination rate, and mortality rate of tested insects. The results showed that Bb22 had the fastest growth rate and Bbz2 displayed the highest conidial production and germination rate. Furthermore, Bb324 showed the highest pathogenicity to the second-instar larvae of A. ipsilon. At 8 days after infection, Bb324 caused a corrected mortality of 70.37%, which was significantly higher than those of other fungal strains. The median lethal time (LT₅₀) of Bb324 was 4.40 days, which was significantly shorter than the LT₅₀ in other strains. The median lethal concentration (LC₅₀) of Bb324 after an 8-day infection was calculated as 2.92×10⁷ conidia/mL. These results indicated that Bb324 has strong pathogenicity towards the second-instar larvae of A. ipsilon, therefore the strain has the potential as a microbial agent for biological control of A. ipsilon in tobacco fields.