Sources of Rhizoctonia solani and Pythium spp. in a Bedding Plant Greenhouse. C. T. Stephens, Former Research Associate, Department of Plant Pathology, Ohio State University, Columbus, and Ohio Agricultural Research and Development Center, Wooster 44691. L. J. Herr, A. F. Schmitthenner, and C. C. Powell, Professors, Department of Plant Pathology, Ohio State University, Columbus, and Ohio Agricultural Research and Development Center, Wooster 44691. Plant Dis. 67:272-275. Accepted for publication 27 July 1982. Copyright 1983 American Phytopathological Society. DOI: 10.1094/PD-67-272.

A greenhouse operation in Ohio was studied to determine the sources of damping-off pathogens and their mode of dissemination to bedding plants. Pythium spp. were isolated from steam-treated soil, but neither Pythium spp. nor Rhizoctonia solani were recovered from the other components of the potting soil mix. Both Pythium spp. and R. solani were isolated from dust and soil mix particle samples collected from walkways, floors, and beds within the greenhouse and also from used seedling flats. When infested dust and soil mix particle samples were sprinkled on flats of seedlings, damping-off occurred. Sources of inoculum were present in this bedding plant greenhouse despite the use of soil steaming and routine sanitation procedures.