ABSTRACT
The pathogenicity of three isolates of Metarhizium anisopliae and two isolates of Beauveria bassiana originating from different insect species and localities was tested against housefly larvae. Only one isolate of M. Anisopliae [Ma23] and two isolates of B. bassiana [Bb2 and Bb108] significantly reduced the percentage of emerging adults. At the highest tested concentration 107 spores/ml, the reduction in the percentage of adult emergence was 93.8%, 61.3% and 49% for Bb2, Ma23 and Bbl08, respectively. Based on the LC50 values, Bb2 was the most virulent isolate, followed by Ma23 and Bbl08. The ability of adult flies to pick up conidiospores from contaminated media and the possibility of isolate recycling through cadavers of fungus-killed adults were also investigated. The results showed that 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 Bbl08, respectively, sporulated under high relative humidity conditions