Biocontrol of Plant Diseases Laboratory, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, MD 20705-2350
Commercially manufactured cellulose granules (Biodac) were mixed with a sticker and fermentor-produced biomass of isolates of Trichoderma spp. and Gliocladium virens to produce a formulation in which chlamydospores in the biomass were “activated” with dilute acid. Activation resulted in the formation of young, actively growing hyphae of the biocontrol fungi within a 2- to 3-day period under no special aseptic conditions. Activated Biodac with biomass of isolates Gl-3, Gl-21, and Gl-32 of G. virens and isolate TRI-4 of T. hamatum applied to soilless mix at a rate of 1.5% (wt/wt) reduced damping-off of eggplant caused by Rhizoctonia solani (R-23) and resulted in stands comparable to that (88%) in noninfested soilless mix. Saprophytic growth of the pathogen was also reduced. The application of either of two activated Biodac formulations to provide the same amount (1.5% with 9.4 mg of biomass per g of Biodac or 0.2% with 75.0 mg of biomass per g of Biodac) reduced preemergence damping-off as well as saprophytic growth of R-23. Also, there was about a 103-fold population increase of Gl-3 and TRI-4 in the soilless mix at the time of plant harvest compared with that provided to the soilless mix at the time of formulation addition. Activated Biodac of Gl-3 also reduced the spread of R-23 in soilless mix when the pathogen was applied at specific foci rather than evenly distributed. The inhibition of pathogen spread significantly reduced the postemergence damping-off of cucumber, eggplant, and pepper seedlings.