First Reports of Sclerotium (Southern) Blight and Rhizoctonia Aerial Blight of Soybeans in Kansas. J. A. Appel, Plant Health Division, Kansas State Board of Agriculture and Department of Plant Pathology, Kansas State University, Manhattan. D. J. Jardine, Department of Plant Pathology, Kansas State University, Manhattan 66506-5502. Plant Dis. 76:539. Accepted for publication 2 November 1991. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0539D.
Soybean (Glycine max (L.) Merr.) plants with characteristic symptoms and signs of southern blight caused by Sclerotium rolfsii Sacc. were found in two of 15 fields in August 1990 in the southeastern Kansas counties of Labette and Cherokee. Incidence of affected plants was 10-50% in localized areas. The fungus formed sclerotia after 13 days in culture and on inoculated soybeans in pots. The fields had a history of soybean or grain sorghum; soil moisture was surplus at planting but fell to low levels during the season. Also in August 1990, soybean plants were received at the Kansas State University Plant Disease Clinic from the northeastern county of Doniphan with leaves that appeared water-soaked or were brown to reddish brown. Lesions varied from I cm in diameter to covering the entire leaf and were present on the petioles and stem. Biopsies of diseased tissue on potato-dextrose agar produced colonies of Rhizoctonia solani Kühn. Frequent rains during late July and August in Doniphan County resulted in adequate to surplus soil moisture and high relative humidity levels.