EFFICACY OF VARIOUS FUNGAL AND BACTERIAL BIOCONTROL ORGANISMS FOR CONTROL OF FUSARIUM-WILT OF TOMATO

Numerous fungi and bacteria, including existing biocontrol strains wit h known activity against soilborne fungal pathogens as well as isolate s collected from the roots and rhizosphere of tomato plants growing in the field, were tested for their efficacy in controlling Fusarium wil t of tomato. Tomato seedlings were treated with the potential biocontr ol agents in the greenhouse and transplanted into pathogen-infested fi eld soil. Organisms tested included nonpathogenic strains of Fusarium spp., Trichoderma spp., Gliocladium virens, Pseudomonas fluorescens, B urkholderia cepacia, and others. Specific nonpathogenic isolates of F. oxysporum and F. solani collected from a Fusarium wilt-suppressive so il were the most effective antagonists, providing significant and cons istent disease control (50 to 80% reduction of disease incidence) in s everal repeated tests. These isolates also were equally effective in c ontrolling Fusarium wilt diseases of other crops, including watermelon and muskmelon. Other organisms, including isolates of G. virens, T. h amatum, P. fluorescens, and B. cepacia, also significantly reduced Fus arium wilt compared to disease controls (30 to 65% reduction), hut wer e not as consistently effective as the nonpathogenic Fusarium isolates . Commercially available biocontrol products containing G. vb ens and I: harzianum (SoilGard and RootShield, respectively) also effectively reduced disease (62 to 68% reduction) when granules were incorporated into pelting medium at 0.2% (wt/vol). Several fungal and bacterial iso lates collected from the roots and rhizosphere of tomato plants also s ignificantly reduced Fusarium wilt of tomato, but were no more effecti ve than other previously identified biocontrol strains. Combinations o f antagonists, including multiple Fusarium isolates, Fusarium with bac teria, and Fusarium with other fungi, also reduced disease, but did no t provide significantly better control than the nonpathogenic Fusarium antagonists alone.