Abstract:Both mycelia and sclerotia of Rhizotonia solani were parasitized by Gliocladium virens (GVP). The parasitized sclerotia were incapable of germination. The metabolites produced by the mycoparasite either inhibited or killed the host fungus. Scanning electron microscopy showed that the mycoparasite tightly coiled around the host fungus, formed appressorium-like structures on the host fungus and presumably achieved its infection by active penetration.