VIEW ARTICLE

Ecology and Epidemiology

Influence of Crop Rotation on Severity of Crown and Brace Root Rot Caused in Corn by Rhizoctonia solani. Donald R. Sumner, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793; D. K. Bell, Department of Plant Pathology, University of Georgia, Coastal Plain Experiment Station, Tifton 31793. Phytopathology 76:248-252. Accepted for publication 16 September 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/Phyto-76-248.

Field microplots were infested with anastomosis group (AG)-2 or AG-4 of Rhizoctonia solani, Rhizoctonialike binucleate fungi or uninfested and planted to 3-yr cropping systems of corn-peanut-corn, peanut-corn-corn, cucumber-cowpea (double-crop)-corn-peanut, or turnip-soybean (double-crop)-corn-peanut. Crown and brace root rot in corn was more severe each year in soil infested with AG-2 than with other treatments, but there were no differences among cropping systems. Corn yield for 3 yr averaged 22% less in soil infested with AG-2 than in uninfested soil. Root and hypocotyl disease severity in peanut was slight each year in all soil treatments, and there were no differences in yield. R. solani AG-2 type 2 was isolated from 1.5-11.0% of the seed from unblemished attached or loose peanut pods during the last 2 yr of the study. Rhizoctonia-like CAG-2 and CAG-4 were isolated from both unblemished and loose peanut pods in the third year. Only AG-4 caused fruit rot and reduced plant stand in cucumber. There were no differences in root disease severity or yield among soil treatments in turnip, cowpea, or soybean. R. solani AG-2 was recovered from soil after the first year of crops but not thereafter. R. solani AG-4 and Rhizoctonia-like CAG-2 and CAG-4 were recovered from soil after each cropping season. Population density of indigenous R. zeae in soil increased more following corn than following peanut during the last 2 yr of the experiment.