Trichoderma harzianum is a well-known biological control agent against fungal plant diseases. In order to select improved biocontrol strains from Trichoderma harzianum CECT 2413, a mutant has been isolated for its ability to produce wider haloes than the wild type, when hydrolysing pustulan, a polymer of beta -1,6-glucan. The mutant possesses between two and four times more chitinase, beta -1,3- and beta -1,6-glucanase activities than the wild type, produces about three times more extracellular proteins and secretes higher amounts of a yellow pigment (cc-pyrone). This mutant performed better than the wild type during in vitro experiments, overgrowing and sporulating on Rhizoctonia solani earlier, killing this pathogen faster and exerting better protection on grapes against Botrytis cinerea.