| The pathogenicity of 15 strains of Beauveria spp., 15 strains of Metarhizium spp., 4 strains of Purpureocillium lilacinum (Thom) and different concentrations of high virulence strains to Solenopsis invicta Buren was determined by the soaking method. The results showed that the Beauveria spp. HHY-B, LCM1, ZYSYE-Y2, Bb034, ZG5, Bb720, Bb040, CP728 and P. lilacinum LYC1 strains exhibited the strongest activity to red imported fire ant workers, the corrected mortality and infection rate varied from 84.70%~98.79% and 72.98%~90.38%, respectively, after inoculation with a concentration of 1.0×10^8 spores/mL for 10 d. Moreover, the corrected mortality and infection rate of S. invicta increased and the median lethal time reduced with the increase of the conidium concentration. The LC50 values of the ZYSYE-Y2, CP728, HHY-B, LCM1, ZG5, Bb040, Bb720, Bb034 and LYC1 strains on day 10 post-treatment were 1.16×10^5, 1.49×10^5, 2.27×10^5, 2.28×10^5, 2.32×10^5, 3.79×10^5, 4.94×10^5, 8.47×10^5 and 3.90×10^6 spores/mL. When inoculated with a concentraion of 1.0×10^7 spores/mL of HHY-B, CP728, ZG5 and Bb040 strains for 10 d, the corrected mortality to red imported fire ant workers were 91.54%, 94.60%, 91.23% and 94.65%, and the infection rates were 82.51%, 91.74%, 85.43% and 80.60%, the median lethal time were 4.22 d, 4.07 d, 3.72 d and 3.68 d, respectively. Collectively, the results indicated that HHY-B, CP728, ZG5 and Bb040 strains of Beauveria spp. could be good candidate strains in S. invicta biological control. |
