41st Annual Meeting of the Society for Invertebrate Pathology
and 9th International Conference on Bacillus thuringiensis

Entomogenous fungi like Metarhizium anisopliae and Beauveria bassiana become attenuated when successively subcultured on artificial media but virulence is restored when they are passaged through an insect host. Exactly why fungi lose virulence when maintained on artificial media is unclear. Nutrition influences the carbon and nitrogen composition of conidia, germination rate and levels of spore bound Pr1; these parameters can to some extent predict the virulence of the inoculum. The importance of these strain-independent parameters as regards the production and quality control of inoculum in commercial systems is discussed.