SUSCEPTIBILITY OF APHIS CRACCIVORA, A GOSSYPII AND MYZUS PERSICAE TO ISOLATES OF ENTOMOPATHOGENIC FUNGI BEAUVERIA BASSIANA, METARHIZIUM ANISOPLIAE AND PAECILOMYCES FUMOSOROSEUS

The pathogenicity of Beauveria bassiana (BbGc), Metarhizium anisopliae (MaPs) and Paecilomyces fumosoroseus (PfPp) was examined against the nymphs of the aphids Aphis gossypii, A. craccivora and Myzus persicae. All of the 3 fungal species were highly infective against A. gossypii at concentrations of 1 x 107, 1 x 106 and 1 x 105 conidia ml1 for B. bassiana, M. anisopliae and P. fumosoroseus, respectively causing 100% nymphal mortality 7 days after inoculation. Relationships between log concentration and probit mortality for all the 3 species were significant (P 0.05). Estimates of EC50 computed for PfPp was consistently the lowest against the 3 aphids, and in conformity with the steeper dosage-mortality slopes. In contrast, BbGc needed higher concentration of inoculum to inflict significant mortality on the 3 aphids. Based on LT50 values, at a comparable dosage of 1 x 107 conidia ml.1, both PfPp and MaPs indicated the shortest time of 2.6 and 3.1 days, respectively to effect 100% mortality on A. craccivora, while all the 3 fungi took 2.6 days or less to completely kill A. gossypii. Myzus persicae was the most unyielding; at a dosage of 1 x 107 conidia ml1 PfPp and MaPs only managed to inflict a maximum of 95% mortality within 3 days, while BbGc was the least virulent. The general, the order of efficacy against the 3 aphid species is PfPp MaPs BbGc.