GREENHOUSE AND FIELD STUDIES ON THE BIOLOGICAL-CONTROL OF TOMATO FRUIT ROT CAUSED BY RHIZOCTONIA-SOLANI

The biocontrol fungi Trichoderma hamatum (TRI-4, Tm-23) and Gliocladium virens (Gl-21) were evaluated in greenhouse and field tests over a 5-year period for their ability to prevent fruit rot of tomato caused by Rhizoctonia solani. In addition, pathogen saprophytic activity and population proliferation by biocontrol agents were evaluated. In the greenhouse, germlings (actively-growing hyphae on bran) and alginate pellets containing biomass of the individual three fungi significantly prevented disease (> 80%), reduced pathogen inoculum (> 75%), and resulted in increases in the population densities of the biocontrol fungi. In the field, these preparations did not significantly prevent fruit rot although pathogen saprophytic activity was reduced by germlings in some tests. Usually, populations of the three isolates proliferated significantly in soil amended with germlings and pellets. In greenhouse and field tests, conidia generally were ineffective in preventing disease, in reducing pathogen inoculum, or in stimulating biocontrol fungi to proliferate. © 1990.