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United States Department of Agriculture

Agricultural Research Service

Title: Suppression of Seedling Damping-off Caused by Pythium Ultimum, Pythium Irregulare, and Rhizoctonia Solani in Container Media Amended with a Diverse Range of Pacific Northwest Compost Sources

Authors
item Scheuerell, Steven - OREGON STATE UNIVERSITY
item Sullivan, Dan - OREGON STATE UNIVERSITY
item Mahaffee, Walter

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 29, 2004
Publication Date: March 1, 2005
Citation: Scheuerell, S.J., Sullivan, D.M., Mahaffee, W.F., 2005. Suppression of seedling damping-off caused by pythium ultimum, pythium irregulare, and rhizoctonia solani in container media amended with a diverse range of pacific northwest compost sources. Phytopathology.95(3):306-315.

Interpretive Summary: 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 P. ultimum, P. irregulare, and R. solani. The composts had been produced from diverse feedstocks and composting technologies, which was reflected in the variability in the measured properties. When mixed with sphagnum peat moss and inorganic aggregates, 66% of the samples significantly suppressed P. irregulare damping-off of cucumber, 64% suppressed P. ultimum damping-off of cucumber, and 17% suppressed R. solani damping-off of cabbage. Pythium damping-off suppression was related to the potential of compost to support microbial activity and a qualitative index of ammonia volatilization. R. solani damping-off suppression was not related to any one compost factor. Currently available compost products could potentially provide acceptable control of damping-off caused by Pythium spp. but there is a need to inoculate with microbial antagonists for the control of R. solani. This research indicates that disease suppression afforded by amending potting media with Pacific Northwest composts is highly variable and needs to be assessed for each compost batch. Additionally, compost sources need to be individually assessed for appropriate uses and application rates because there are a wide range of physical, chemical, and biological properties.

Technical Abstract: 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 P. ultimum, P. irregulare, and R. solani. The composts had been produced from diverse feedstocks and composting technologies, which was reflected in the variability in the measured properties. When mixed with sphagnum peat moss and inorganic aggregates, 66% of the samples significantly suppressed P. irregulare damping-off of cucumber, 64% suppressed P. ultimum damping-off of cucumber, and 17% suppressed R. solani damping-off of cabbage. Pythium damping-off suppression was related to the potential of compost to support microbial activity and a qualitative index of ammonia volatilization. A positive linear relationship was evident between the percent healthy seedlings and compost respiration potential for the 26 compost samples that respired below 3.0 mg CO2/g compost carbon/day, while composts with detectable ammonia volitilization were nonsuppressive. R. solani damping-off suppression was not related to any one compost factor and appeared to be mediated by physio-chemical properties, since heat treatment did not reduce suppression in the bark/dairy-solids compost. Currently available compost products could potentially provide acceptable control of damping-off caused by Pythium spp. but there is need to inoculate with microbial antagonists for the control of R. solani.

Last Modified: 11/27/2014
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