Spore germination and hyphal growth of Beauveria sp. on insect lipids

The effect of cuticular lipids of Ostrinia nubilalis (Hubner) and Melolontha melolontha (L.) spore germination and hyphal growth of entomopathogenous fungi was examined. A Beauveria bassiana strain virulent to O. nubilalis and a Beauveria brogniartii strain virulent to M. melolontha were used. The epicuticular lipid-extract of the host insect did not alter the growth of the corresponding virulent strain measured both as spore germination or hyphal growth. However, the cuticular pentane-extract of M. melolontha inhibited both the hyphal growth and spore germination of the nonpathogenic strain of B. bassiana. The hyphal inhibition was caused mostly by the unsaturated hydrocarbon fraction. Methanol-extracts of both insects inhibited hyphal growth and spore germination of the 2 virulent and nonvirulent strains. Exposure to O. nubilalis lipid extract most strongly inhibited hyphal growth of both strains