Pathogenicity of Beauveria bassiana and Metarhizium anisopliae against Galleria mellonella

The greater wax moth Galleria mellonella L. (Lepidoptera: Pyralidae) is occasionally found in beehives and is a major pest of stored wax. Entomopathogenic fungi have recently received attention as possible biocontrol elements for certain insect pests. In this study, 90 isolates of Beauveria bassiana and 15 isolates of Metarhizium anisopliae were screened for proteases and lipases production. The results showed significant variations in the enzymatic action between the isolates. In the bioassay, the selected isolates evinced high virulence against the 4th instar of the G. mellonella larvae. The isolates BbaAUMC3076, BbaAUMC3263 and ManAUMC3085 realized 100% mortality at concentrations of 5.5 x 10(6) conidia ml(-1), 5.86 x 10(5) conidia ml(-1), and 4.8 x 10(6) conidia ml(-1), respectively. Strong enzymatic activities in vitro did not necessarily indicate high virulence against the tested insect pest. The cuticle of the infected larvae became dark and black-spotted, indicating direct attack of fungus on the defense system of the insects. The LC50 values were 1.43 x 10(3), 1.04 x 10(5) and 5.06 x 10(4) for Bba3263AUMC, Bba3076AUMC and Man3085AUMC, respectively, and their slopes were determined by computerized probit analysis program as 0.738 +/- 0.008, 0.635 +/- 0.007 and 1.120 +/- 0.024, respectively.