A Quantifiable Type of Inoculum of Rhizoctonia solani. A. H. C. Van Bruggen, Graduate Research Assistant, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. P. A. Arneson, Associate Professor, Department of Plant Pathology, Cornell University, Ithaca, NY 14853. Plant Dis. 69:966-969. Accepted for publication 8 April 1985. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-966.

Production of sclerotia of Rhizoctonia solani was compared on six types of substrates in vitro. Autoclaved green bean pods were the most efficient substrate. About 1 million sclerotia measuring 300–710 μm in diameter were produced on 1 kg of frozen cut beans. The viability of sclerotia on potato-dextrose agar was greater with increasing size of sclerotia. Similarly, the ability of large sclerotia to grow on sand and infect a bean hypocotyl piece was better than that of small sclerotia. Sclerotia formed on bean pods were more vigorous than sclerotia of the same size produced on bean leaves. Only growth of small sclerotia from bean leaves was stimulated by the presence of a hypocotyl piece.