The effect of crucifer epicuticular waxes and leaf extracts on the germination and virulence of Metarhizium anisopliae conidia

Leaves of members of the Cruciferae influence the germination of the entomo genous fungus Metarhizium anisopliae. The percentage germination of conidia on reconstituted epicuticular waxes of oilseed rape, Chinese cabbage, and turnip was influenced by the solvent used, the plant species, and the age o f the leaf. The epicuticular waxes contain a mixture of stimulatory and inh ibitory compounds. Germination was more rapid and greater on the surfaces o f dewaxed than intact leaves suggesting that epicuticular waxes contain fun gistatic compounds and/or act as a barrier to the leaching of nutrients. Su rface leachates and soluble extracts of leaves increased percentage germina tion of conidia and the virulence of M. anisopliae to the mustard beetle, P haedon cochleariae. Plant extracts stimulated germination more than yeast o r starch extract. Formulation of conidia in leachates or leaf extracts incr eased the virulence of M. anisopliae. Germination increased on insect cutic le that were pretreated with leaf extracts/leachates, suggesting that the i nsect cuticle will adsorb or sequester nutrients.