The virulence of Beauveria bassiana and Metarhizium anisopliae strains against Spodoptera exigua larvae

4 strains of Beauveria bassiana(Bals.) Vuill and 5 strains of Metarhizium anisopliae(Metsch.) Sorokin were tested for pathogenicity to Spodoptera exigua(Hubner) larvae.The results indicated that the strains B187 and Ma1291-2 possessed a stronger virulence to S.exigua larvae inoculated with(1.0 ± 0.5) × 108conidia·mL-1for 8 days.The correct mortality and cadaver rate of B187 treating were(93.21 ± 3.20)% and(84.76 ± 1.47)%,and those of Ma1291-2 were just(94.70 ± 0.68)% and(88.06 ±1.75)% respectively.For the two strains,the half lethal times(LT50) were 5.57 d and 5.33 d respectively.A time-dose-mortality model was employed to estimate parameters of time and dose,which showed that the time with a stronger lethal effect of the two strains on S.exigua larvae was 4-5 days after inoculation.The half lethal concentrations(LC50) of the two strains to larvae on the6 th day were 6.41 × 106conidia·mL-1and 8.49 × 105conidia·mL-1respectively.It suggested that the two strains had important application potential.