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Disease Note.

First Report of Red Crown Rot on Soybeans in Mississippi. K. W. Roy, Mississippi State University, Mississippi State, MS 39762. K. S. McLean, G. W. Lawrence, M. V. Patel, and W. F. Moore. Mississippi State University, Mississippi State, MS 39762. Plant Dis. 73:273. Accepted for publication 19 January 1989. Copyright 1989 The American Phytopathological Society. DOI: 10.1094/PD-73-0273F.

Red crown rot of soybeans (Glycine max (L.) Merr.) caused by Cylindrocladium crotalariae (Loos) Bell & Sobers (teleomorph Calonectria crotalariae (Loos) Bell & Sobers) was first observed in a single field in Noxubee County, Mississippi, in 1986. Symptoms included leaf chlorosis and interveinal necrosis, defoliation, reddening of the crown, and root rot. Perithecia were found on many infected stems. C. crotalariae was isolated from root and stem tissues but not from mature seeds. Koch's postulates were fulfilled by growing plants in soil artificially infested with C. crotalariae in the greenhouse. Since 1986, the disease has spread to six new fields within a 5-km radius of the original site. In most fields each year, small patches of infected plants were randomly distributed and yield was not affected. In a 50-ha field in 1988, however, infected plants were uniformly distributed and yield loss was estimated at 25-30%