Rhizoctonia Web Blight of Soybeans in Puerto Rico. P. R. Hepperly, Assistant Professor, Department of Crop Protection, University of Puerto Rico, Mayaguez. J. S. Mignucci, Assistant Professor, Department of Crop Protection, University of Puerto Rico, Mayaguez; J. B. Sinclair, Professor, Department of Plant Pathology, R. S. Smith, former Assistant Professor, and W. H. Judy, former Associate Professor, Department of Agronomy, University of Illinois at Urbana-Champaign 61801. Plant Dis. 66:256-257. Accepted for publication 1 June 1981. Copyright 1982 American Phytopathological Society. DOI: 10.1094/PD-66-256.

Web blight caused by Rhizoctonia solani is reported for the first time in Puerto Rico. Disease development was followed in two 0.1-ha fields of Davis soybeans (Glycine max), one sprayed weekly with benomyl (0.25 kg/ha) and the other not sprayed. Symptoms appeared before the full-green stage (R₅) in the unsprayed field and after the full-green pod stage (R₆) in the sprayed plot. The number of disease foci and their size increased with increasing soybean maturity, particularly between the yellow-pod (R₇) and the mature-pod (R₈) stages. In the unsprayed field, R. solani was isolated from 5% of the seeds harvested from web-blighted plants but was not recovered from seeds of adjacent plants without web blight.

Keyword(s): aerial blight, seed quality.