VIEW ARTICLE

Disease Control and Pest Management

The Role of Microorganisms in the Suppression of Rhizoctonia solani in Container Media Amended with Composted Hardwood Bark. E. B. Nelson, Graduate research associate, Department of Plant Pathology, Ohio State University, Wooster 44691; H. A. J. Hoitink, professor, Department of Plant Pathology, Ohio State University, Wooster 44691. Phytopathology 73:274-278. Accepted for publication 21 April 1982. Copyright 1983 The American Phytopathological Society. DOI: 10.1094/Phyto-73-274.

Suppression of Rhizoctonia damping-off in container media amended with mature (>11-wk-old) composted hardwood bark (CHB) was eliminated by heat (60 C) and gamma radiation (275 krad). Media amended with green (<11-wk-old) CHB were only slightly suppressive and heating had no effect on the resulting incidence of damping-off. Suppression could be reestablished in heated mature CHB media by adding 10% (v / v) unheated mature CHB or 10⁷ colony-forming units (CFU) of Trichoderma harzianum per gram of container medium. Propagules of Rhizoctonia solani were killed rapidly in unheated media containing mature CHB and in heated mature CHB media amended with T. harzianum, but a high percentage of propagules remained viable in media amended with either green or heat-treated mature CHB. Results suggest that suppression of Rhizoctonia damping-off of radish in container media amended with mature CHB is induced by microbial activity, whereas the low level of suppression observed in green CHB-amended media may involve chemical inhibitors.