Survival of uninucleate Rhizoctonia species during composting of forest nursery waste

Forest nursery waste was composted with and without different nitrogen sources in 300 litre composts. Uninucleate Rhizoctonia (teleomorph Ceratobasidium bicorne ) was selected as a model pathogen for testing the survival of pathogens during composting. Hyphal culture of the pathogen was mixed with waste material and buried in nylon mesh bags in the composts. Temperature, water content, pH and volume reduction were monitored during the composting period. Carbon, nitrogen and phosphorus concentrations were determined in the initial compost materials. After composting, the pathogen was baited with Norway spruce seedlings, and damping-off due to uninucleate Rhizoctonia was recorded. None of the seedlings showed any symptoms of damping-off in the treatment in which forest nursery waste was composted with cutter-chip bedded horse manure, indicating eradication of the pathogen. The survival of the test pathogen in the other treatments is a risk for the future use of the composted material in forest nurseries.