Effect of entomofungal pathogens on mortality of three aphid species

The pathogenicity of twelve fungal isolates belonging to Beauveria bassiana (Bals.) Vuill., Metarhizium anisapliae (Metschinikoff) Sorokin and Verticillium lecanii (Zimmerman) against Aphis craccivora Koch, Aphis gossypii Glover and Rhopalosiphum maidis Fitch was studied using detached leaf bioassay technique. AH twelve isolates of the three fungi were found to be pathogenic to A. craccivora and A. gossypii at a concentration of 1x 10′ spores/ml, All isolates except Bb3 and Bb4 of B. bassiana were pathogenic to if. maidis. The mortality ranged from 2 to 74 per cent in A. craccivora, 14 to 80.8 per cent in A. gossypii and 6 to 50 per cent in R. maidis. Bb5a isolate of B, bassiana caused highest per cent mortality in A, gossypii (80.8%) and S, maidis (50%) indicating its broad spectrum action. VII isolate of K lecanii recorded maximum mortality (80.8%) of A. craccivora. R. maidis was relatively less susceptible to the three fungi than A. craccivora and A. gossypii. The LC₅₀ of Bb5a for three days old nymphs of A. gossypii was 6.57x10⁵ spores/ml. The LX₅₀of Bb5a for three days old nymphs of A, gossypii was highest (9.67 days) for the lowest dose of 10⁶ spores/ml, which decreased with increasing concentration. The highest dose 10⁹spores/ml recorded the lowest LT₅₀ of 1.76 days.