Evaluation of commercial products for microbial control of soil-borne plant diseases

Abstract

Five microbial products (SUPRESIVIT, active microbial ingredient Trichoderma harzianum; TRI 002, T. harzianum; ECOFIT, T. viride; SOILGARD, Gliocladium virens; PROTUS, Talaromyces flavus) claimed by their manufacturers to protect against soil-borne plant pathogens were tested in the greenhouse for efficacy against Pythium ultimum on cucumber and Rhizoctonia solani on peas. With the exception of ECOFIT, that was applied as a soil drench directly after planting, the products were mixed together with the pathogens into the potting substrate immediately before planting. Under these conditions, considerable variation in efficacy was observed between the products. Against R.solani, SOILGARD was as efficacious as the chemical standard pencycuron. Also, SOILGARD was the only biocontrol product that gave significant control of P. ultimum. The other biocontrol products showed some efficacy against the two pathogens, but in most cases the level of disease control was not statistically significant. A comparison of performance in heat-treated and nontreated potting substrate indicated that, in the case of R. solani, activity of all biocontrol products was enhanced by heat-treatment. On the contrary, control of P. ultimum tended to be weaker in heat-treated than in nontreated potting medium. When laboratory preparations based on the active microbial ingredients from SUPRESIVIT and SOILGARD were applied at equal rates, control of R. solani by the SOILGARD-preparation was superior to that by the SUPRESIVIT-preparation, despite a higher number of propagules in applied amounts of the latter. The reasons for the observed variability in efficacy of the different biocontrol products are discussed.