VIEW ARTICLE

Disease Control and Pest Management

Effects of Organic Matter Decomposition Level and Cellulose Amendment on the Inoculum Potential of Rhizoctonia solani in Hardwood Bark Media. Y. R. Chung, Graduate research associate, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691; H. A. J. Hoitink(2), W. A. Dick(3), and L. J. Herr(4). (2)(4)Professors, Department of Plant Pathology, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691; (3)Associate professor, Department of Agronomy, The Ohio State University, Ohio Agricultural Research and Development Center, Wooster 44691. Phytopathology 78:836-840. Accepted for publication 25 January 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/Phyto-78-836.

Container media amended with fresh hardwood bark (~ 45% cellulose, w/w) were conducive to Rhizoctonia damping-off of radish. Those amended with hardwood bark compost were suppressive. Significantly higher cellulase activity was present in the fresh bark medium colonized by R. solani than in the bark compost medium. The population of R. solani increased in the fresh bark but not in the bark compost medium. Addition of low levels of cellulose (5%, w/w) to the bark compost medium decreased damping-off. High levels of cellulose (20%, w/w) established high cellulase levels in the Rhizoctonia-infested bark compost media, increased the population of R. solani, and negated suppression. Even in the presence of a suppressive microflora, the high cellulose amendment increased conduciveness. We conclude that high cellulose levels increase the inoculum potential of R. solani, resulting in increased damping-off severity.