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Disease Note.

First Report of Sheath Blight (Rhizoctonia solani) on Field Corn in Arkansas. M. C. Hirrel, Southeast Research and Extension Center, Monticello, AR 71655. F. N. Lee, J. L. Dale, and D. E. Plunkett. Rice Research and Extension Center, Stuttgart, AR 72160; Department of Plant Pathology, University of Arkansas, Fayetteville 72701; and Jefferson County Cooperative Extension Service, Pine Bluff, AR 71611. Plant Dis. 72:644. Accepted for publication 2 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0644B.

Symptoms of sheath blight caused by Rhizoctonia solani KUhn were found on field corn (Zea mays L.) in east central Arkansas. Reddish eyes pot lesions with dark red to purple margins were observed on stalks starting near the soil line and developing upward to 2 m. Prolific sclerotial development occurred on older lesions of leaf sheaths, ear husks, and silks. The fungus penetrated leaf sheaths to the rind and appeared as a yellow-green discoloration with a thin black border. A multinucleate isolate of R. solani was recovered from infected plants and tentatively identified as a sasakii form on the basis of positive pathogenicity tests on rice and soybean. Further characterization of the fungus based on anastomosis group identification is pending. Disease developed in irrigated fields with over 100 units of N fertilizer and a history of rice production within the past 1-6 yr. Disease incidence was measured for three varieties and averaged 45% for Asgrow 2570, 50% for Ringaround 1502, and 37% for Pioneer 3165. Varieties Dekalb T 1100, Dekalb 656, Pioneer 3165, Pioneer 3124, Pioneer 3358, and Funks 1502 were observed to be infected, but no incidence values were recorded.