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Ecology and Epidemiology

Survival of Rhizoctonia spp. and Root Diseases in a Rotation of Corn, Snap Bean, and Peanut in Microplots. Donald R. Sumner, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793-0748; Durham K. Bell, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793-0748. Phytopathology 84:113-118. Accepted for publication 19 October 1993. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/Phyto-84-113.

The ability of several basidiomycetous fungi occurring naturally in Georgia coastal plain soils to survive and control Rhizoctonia solani anastomosis group 2 (AG-2) and AG-4 in field microplots was determined. Undisturbed profiles of soil in field microplots were fumigated with metamsodium and infested with Rhizoctonia solani AG-2-1, AG-2-2, or AG-4, or with binucleate Rhizoctonia spp. CAG-2, CAG-3, CAG-4, or CAG-5. A corn-peanut rotation was then grown for 3 yr. In a second experiment, microplots were infested with AG-4 and AG-2 alone or in combination with the potential antagonists CAG-2, CAG-4, CAG-5, Laetisaria arvalis, and an unidentified orange basidiomycetous fungus. Two-year rotations of corn-snap bean (double crop)-peanut or peanut-corn-snap bean were grown for 3 yr. CAG-4 reduced stunting and leaf chlorosis induced by AG-2-2 in corn in the first year but not in the third year after infestation. In the third year, the orange basidiomycetous fungus and CAG-5 increased the yield of corn with low levels of crown and brace root rot. Root and hypocotyl rot was not decreased, and yield of peanut and snap bean were not increased by the antagonists. Population densities of all antagonists in infested soil remained at levels greater than in noninfested soil for 310 mo, but populations were variable 1932 mo after infestation. Antagonists were isolated from 010% and AG-2-2 from 07% of the loose, sound, or decayed peanut pods each year. CAG-4, CAG-5, and the unidentified orange basidiomycetous fungus all show potential for surviving in soil and reducing deleterious effects of crown and brace root rot in corn in multiple-cropping systems in rotation with peanut.