Application of Trichoderma and Gliocladium in alginate pellets for control of Rhizoctonia damping-off

Alginate pellets were prepared from wet fermentor biomass of 11 isolates of Trichoderma spp. and Gliocladium virens, with wheat bran as a food base carrier. Pellets with eight of the isolates reduced survival (34‐78%) of Rhizoctonia solani in infested beet seed in soil. Pellets containing a T. harzianum isolate (Th‐58) and a T. hamatum isolate (TRI‐4) were the most effective. All isolates significantly reduced growth of the pathogen from infested beet seed into natural soil. Populations of isolates proliferated in soil to 106−1011 colony‐forming units/g (cfu) from propagules within the pellets. Pellets with TRI‐4 reduced pathogen survival and growth (>70%) in six different soils and were effective against six R. solani isolates in a natural loamy sand. Survival of R. solani in infested beet seed was not reduced when TRI‐4 pellets were added to soil 1‐6 weeks before the pathogen; however, saprophytic growth was prevented. Small amounts of biomass (3.0–7.5 g wet weight) in pellets were as effective as a large amount (300 g) in suppressing the pathogen. The storage of pellets for more than 6 weeks at 5 or 25C reduced their effectiveness against R. solani. Pellets prepared with four and three of the 11 isolates prevented damping‐off of cotton and sugar beet in the greenhouse, respectively.