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Etiology

Rhizoctonia spp. Associated with Brown Patch of Saint Augustinegrass. B. Hurd, Former graduate teaching assistant, Department of Plant Sciences, Texas A&M University, College Station 77843; M. P. Grisham, assistant professor, Department of Plant Sciences, Texas A&M University, College Station 77843. Phytopathology 73:1661-1665. Accepted for publication 1 July 1983. Copyright 1983 American Phytopathological Society. DOI: 10.1094/Phyto-73-1661.

Isolates of Rhizoctonia from St. Augustinegrass (Stenotaphrum secundatum) displaying brown patch symptoms were either R. solani anastomosis group 2 type 2 (AG2-2) or unidentified Rhizoctonia species with binucleate hyphal cells. In the laboratory, R. solani AG2-2 isolates produced brown patch symptoms on stolon sections of cultivar Texas Common St. Augustinegrass at 24 C. An R. solani AG2-2 from St. Augustinegrass also caused postemergence damping-off in two cultivars of Festuca arundinacea and pre- and postemergence damping-off in five cultivars of Lolium perenne. No seedling disease was produced in two cultivars of Poa pratensis, one cultivar of P. trivialis, or one cultivar of Agrostris palustris. Isolates of the binucleate Rhizoctonia species were not pathogenic on cultivar Texas Common St. Augustinegrass or on any cool-season turfgrass tested. Symptom severity and rate of disease development varied among four cultivars and 11 accessions of St. Augustinegrass inoculated with R. solani AG2-2.