Trichoderma harzianum:A Biocontrol Agent Effective AgainstSclerotium rolfsiiandRhizoctonia solani

Abstract

An isolate of T. harzianum capable of lysing mycelia of S. rolfsii and R. solani was isolated from a soil naturally infested with those pathogens. In culture, T. harzianum grew better than S. rolfsii and invaded its mycelium under growth conditions adverse to the pathogen; high pentachloronitrobenzene concentrations, high pH levels, or low temperatures. Under greenhouse conditions, incorporation of the wheat-bran inoculum preparation of T. harzianum in pathogen-infested soil significantly reduced bean diseases caused by S. rolfsii, R. solani or both, but its biocontrol capacity was inversely correlated with temperature. The wheat bran preparation of T. harzianum increased growth of bean plants in a noninfested soil and it controlled S. rolfsii more efficiently than a conidial suspension of the same antagonist. An uninoculated wheat bran preparation increased disease incidence. In naturally infested soil, wheat bran preparations of T. harzianum inoculum significantly decreased diseases caused by S. rolfsii or R. solani in 3 field experiments with beans, cotton, or tomatoes, and they significantly increased the yield of beans.