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Disease Note.

Rhizoctonia solani AG-l-1A and AG-2-2 IIIB Cause Brown Patch on Tall Fescue and Creeping Bentgrass in Ohio. L. J. Merr, Ohio Agricultural Research and Development Center; The Ohio State University, Wooster 44691. M. M. Fulton, Agricultural Technical Institute, The Ohio State University, Wooster 44691. Plant Dis. 79:1186. Accepted for publication 21 August 1995. Copyright 1995 The American Phytopathological Society. DOI: 10.1094/PD-79-1186E.

Previously, both Rhizoctonia solani Kuhn and R. zeae Voorhees on creeping bentgrass (Agrostis palustris Huds.) and R. solani on tall fescue (Festuca arundinacea Schreb.) have been reported to cause brown patch in Ohio. Recently, field samples of diseased tall fescue (tf) and creeping bentgrass (cbg) were assayed for R. solani and Ihe isolates obtained were identified to anastomosis-intraspecific grouping (AG-ISG). AG-ISGs are genetically distinct and exhibit varying degrees of host specialization and fungicide sensitivity (2). Leaf lesions of tf yielded AG-l-IA isolates, whereas cbg leaves and crowns yielded AG-2-2 IIIB. AG-1-1A has been reported on tf in Arkansas, Nebraska, and now Ohio; there have been no reports of AG-2-2 IIIB. Seven AG-1-1A isolates from tf and six AG-2-2 IIIB isolates from cbg were assayed for pathogenicity on both grasses in water agar plates at 24C and in greenhouse pots at 24 to 32C; planted, infested after 14 days, given 7 days in moist chamber, and evaluated 4 weeks later. Both AG-ISGs were pathogenic on both tf and cbg in both assays. Possibly similar results of Martin and Lucas (1) with R. solani isolates, given only as AG-1 and AG-2, were pathogenic on both tf and cbg. Factors affecting host range and field occurrence of these two AG-ISGs need to be resolved.

References: (1) S. B. Martin and L. T. Lucas. Phytopathology 74:170, 1984. (2) A. Ogoshi. Fitopathol. Bras 10:371. 1985.