First Report of Stem Canker on Soybeans in Arkansas. M. C. Hirrel, Department of Plant Pathology, University of Arkansas-SEREC, Monticello 71655. T. L. Kirkpatrick, Department of Plant Pathology, University of Arkansas-SWREC, Hope 71801. Plant Dis. 70:78. Accepted for publication 12 September 1985. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-78b.
Diaporthe phaseolorum (Cke. & Ell.) Sacc. f. sp. caulivora (Athow & Caldwell) Kulik, the causal agent of stem canker, was isolated from soybean (Glycine max (L.) Merr.) cultivars Bragg and Coker 237 in fields near Caddo Valley, Clark County, Arkansas, on 28 September 1984. Disease incidence was only 5–10%, but many plants had 60–80% top dieback from stem-girdling cankers. Tan cankers with red-purple margins were observed extending down the stem from lower leaf nodes. Confirmation was made by W. S. Gazaway and J. Mullen of Auburn University. Wound inoculation of the cultivar Bragg and the breeding line J77-339 was used to complete Koch’s postulates with Diaporthe and its Phomopsis anamorph.