Pathogenecity of Two Beauveria Bassiana Indigenous Isolates towards the Greater Wax Moth Galleria Mellonella L. Larvae in Egypt

Bioassays were carried out in the laboratory to determine the virulence of two Beauveria bassiana indigenous isolates on the greater wax moth Galleria mellonella. LC50 and LT50 values were taken as indices for the efficacy of fungal isolates, designated as Bb1 and Bb2, collected from Ismailia governorate in Egypt and isolated from soil and trap larvae of G. mellonella, respectively. The larvae of G. mellonella were more susceptible to Bb2 than to Bb1 isolate. Four days post-exposure to the fungal treatment, the LC50 value of Bb1 was over 4000 times higher than that of Bb2. At a concentration of 2.5 x10 spores/ml, the LT50 of larvae contaminated with Bb1 was 10 days, whereas for Bb2, significantly lower LT50 of 6.4 days (P<0.05) was observed. The variability of the virulence and its relationship to either germination and growth of the fungus or defence mechanism of the insect are discussed in the current work.