Biocontrol of damping-off of greenhouse-grown crops caused by Rhizoctonia solani with a formulation of Trichoderma spp.

Abstract

A biocontrol formulation system which did not require sterile conditions during preparation consisted of mixing vermiculite, powdered wheat bran, and dry fermentor-produced biomass (FB) of isolates of Trichoderma and Gliocladium (VBA–FB) with 0.05 M HCl and drying the mixture. Before addition to Rhizoctonia solani-infested soilless mix (Redi-Earth), the dry preparation (VBA–FB) was activated by remoistening with 0.05 N HCl. After 2–3 d of incubation at 23–25°C, the development of young, actively growing hyphae was stimulated in the activated VBA–FB. Controls did not contain FB. Applied to soilless mix at a rate of 1.0% (w/w, dry weight), activated VBA–FB of two out of six isolates tested reduced damping-off of pepper seedlings after 4 weeks of growth to yield stands comparable to those in the noninfested control (85%). Activated VBA–FB of these two isolates, T. hamatum (TRI-4) and T. virens (Gl-3), also reduced damping-off of eggplant, zinnia, cucumber, and cabbage caused by isolate R-23 of R. solani. Generally, G1-3 was more effective than TRI-4. Activated VBA–FB of TRI-4 and Gl-3 also reduced damping-off of cucumber caused by other isolates (195, NG-2, DPR-1) of R. solani, anastomosis group AG-4. Rates as low as 0.13% of formulations of TRI-4 and Gl-3 prevented cucumber damping-off caused by R-23. However, a rate of 0.5% was necessary to yield plant stands comparable to those in the noninfested control. All rates of both isolates reduced the saprophytic growth of R-23 in soilless mix to various degrees. Application to soilless mix of activated VBA–FB of both isolates stimulated populations (colony forming units) at plant harvest about 100-fold compared to the amount added at the time of application. Generally, additions of activated VBA–FB of TRI-4 or Gl-3 to pathogen-infested soilless mix 2 weeks before planting or at the time of planting resulted in damping-off control in pepper and cucumber.