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Etiology

Characterization and Pathogenicity of Rhizoctonia spp. and Binucleate Rhizoctonia-like Fungi from Turfgrasses in North Carolina. S. B. Martin, Graduate research assistant, Department of Plant Pathology, North Carolina State University, Raleigh 27650, Present address: New York State Agricultural Experiment Station, Geneva 14456; L. T. Lucas, professor, Department of Plant Pathology, North Carolina State University, Raleigh 27650. Phytopathology 74:170-175. Accepted for publication 4 August 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-170.

Fungi with Rhizoctonia-like mycelial states were isolated from diseased cool- and warm-season turfgrasses in North Carolina and the species were identified when possible. Fungi were identified as R. solani, R. cerealis, R. zeae, or binucleate Rhizoctonia-like fungi (RLF). Isolates of R. solani were assigned to anastomosis groups (AG) 1, 2, 4, or 5 or could not be assigned to anastomosis groups because of lack of anastomosis with AG tester isolates. Most isolates of R. solani induced foliar blight symptoms on cool-season grasses, but in greenhouse inoculations one isolate from symptomatic bermudagrass (Cynodon dactylon × C. transvaalensis ' Tifton 419' ) induced a crown rot similar to symptoms observed in the field. Similar inoculations with isolates of R. solani indicated greater virulence on cool-season grasses than warm-season grasses with the exception of the bermudagrass crown-rotting isolate. Isolates of R. cerealis were obtained during periods of cool, damp weather and were associated with a foliar chlorosis of creeping bentgrass (Agrostis palustris). Rhizoctonia zeae was isolated three times from diseased tall fescue (Festuca arundinacea) and once from creeping bentgrass during hot weather. Isolates of R. zeae were as virulent on tall fescue and Kentucky bluegrass (Poa pratensis) as the R. solani isolates tested in greenhouse experiments under hot weather conditions.