Mutants of entomopathogenic fungi that germinate and grow at reduced water activities and reduced relative humidities are more virulent to Nephotettix virescens (green leafhopper) than the parental strains

A method was developed to isolate mutants of Metarhizium anisopliae and Paecilomyces farinosus able to germinate and grow at lower water activities ( a w) and relative humidites than the parental strains. Producing blastospores of these mutants in cultures grown on low water activity medium ( a w = 0·969) further increased their ability to germinate at low a w. At a relative humidity of 96–98%, some of the mutants were more virulent against green leafhopper than the parental strains, i.e. they had reduced LT 50 values.