Pathogenicity of two entomopathogenic hyphomycetes, Beauveria bassiana and Metarhizium anisopliae, to the housefly Musca domestica L.

The pathogenicity of three isolates of Metarhizium anisopliae and two isolates Beauveria bassiana originating from different insect species and localities was tested against housefly larvae. Only one isolate of M. anisopliae (Ma23) and the two isolates of B. bassiana (Bb2, Bb108) significantly (P<0.05) reduced the percentage of emerging adults. At the highest tested concentration 10(7) spores/ml. the reduction in the percentage of adult emergence was 93.8%. 61.3% and 49% for Bb2. Ma23 and Bb108. respectively. Based on the IC50 values Bb2 was the most virulent isolate followed by Ma23 and Bb108, (1.13. 1.7 and 4 x 10(6). respectively). The ability of adult flies to pick up conidiospores from contaminated media as well as the possibility of isolate recycling through cadavers of fungus-killed adults were also investigated. Adults were able to pick up conidiospores from the contaminated media. All contaminated adult cadavers subsequently sporulated when placed under high relative humidity conditions. When adult flies were exposed to mycotised cadavers 12. 75 and 76% of the adults exposed to Bb2, Ma23 and Bb108, respectively sporulated under high relative humidity conditions.