Suppression of seedling damping-off caused by Pythium ultimum, P irregulare, and Rhizoctonia solani in container media amended with a diverse range of Pacific northwest compost sources

Suppression of seedling damping-off disease caused by Pythium spp. and Rhizoctonia solani is a potential benefit of formulating soilless container media with compost. Thirty-six compost samples from Pacific Northwest commercial composting facilities were analyzed for a number of physical, chemical, and biological properties. including Suppression of damping-off caused by Pythium ultimum. P irregulate. and R. solani. The samples were produced from diverse feedstocks and composting technologies: this was reflected in a large degree of variability in the measured properties. When mixed with sphagnum peat moss and inorganic aggregates, 67% of the compost samples significantly suppressed P. irregulare damping-off of cucumber, 64% suppressed P ultimum damping-off of cucumber, and 17% suppressed damping-off of cabbage caused by R. solani. Suppresion Of Pythilium damping-off was related to the potential of compost to Support microbial activity and a qualitative index of ammonia volatilization. Suppression of Rhizoctonia damping-off was not related to any One compost factor. Currently available compost products potentially Could provide commercially acceptable control of damping-off caused by Pyhtium spp.. but it is necessary to fortify composts with microbial antagonists for the control of R. solani.