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Pathogenicity of Rhizoctonia solani AG-2-2 and Ophiosphaerella herpotricha on Zoysiagrass. D. E. Green II, Graduate Research Assistant, Department of Horticulture, Forestry and Recreational Resources, Kansas State University, Manhattan 66506-5502. J. D. Fry, J. C. Pair, and N. A. Tisserat. Assistant Professor, Professor, Department of Horticulture, Forestry and Recreational Resources, and Associate Professor, Department of Plant Pathology, Kansas State University, Manhattan 66506-5502. Plant Dis. 77:1040-1044. Accepted for publication 24 June 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1040.

Rhizoctonia solani AG-2-2 was consistently associated with a large patch disease of zoysiagrass in Kansas, Missouri, and Tennessee. In field inoculation tests, patch symptoms developed during both spring and fall as the turfgrass was entering or breaking winter dormancy. The fungus infected and colonized leaf sheaths, but not stolons or roots, at 1030 C, with optimal infection at 2025 C. Rhizoctonia large patch development was suppressed in summer by thatch temperatures exceeding 30 C. Ophiosphaerella herpotricha was isolated infrequently from diseased zoysiagrass but did cause extensive root discoloration and weight loss in the greenhouse and circular dead patches 1 yr after field inoculations.

Keyword(s): binucleate Rhizoctonia spp., Gaeumannomyces incrustans, spring dead spot, Zoysia japonica, Zoysia tenuifolia.