VIEW ARTICLE

Disease Detection and Losses

Crop Losses in Corn Induced by Rhizoctonia solani AG-2-2 and Nematodes. Donald R. Sumner, Department of Plant Pathology, University of Georgia and U.S. Department of Agriculture, Agricultural Research Service, Coastal Plain Experiment Station, Tifton, GA 31793-0748; Norman A. Minton, Department of Plant Pathology, University of Georgia and U.S. Department of Agriculture, Agricultural Research Service, Coastal Plain Experiment Station, Tifton, GA 31793-0748. Phytopathology 79:934-941. Accepted for publication 15 February 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1989. DOI: 10.1094/Phyto-79-934.

Field corn was grown for 3 yr in a Fuquay loamy sand soil infested with Rhizoctonia solani AG-2-2. Grain yields averaged 6,890 and 8,760 kg/ha, with high and low inoculum levels, respectively, compared with 9,890 kg/ha for noninfested plots. Yields were reduced 47, 42, and 8% in soil infested with the high inoculum level and 15, 19, and 1% with the low inoculum level from the first through the third years, respectively, compared with noninfested soil. The percentage of crown and brace roots with terminal decay 7–8 wk after planting had a highly significant effect on grain yield each year. The root disease index, the total number of crown and brace roots per plant, the number of roots without lesions, and nematodes explained 44–47% of the variation in yield each year.