Survey of Reproductive Forms of Rhizoctonia solani on Soybean in Louisiana. X. B. Yang, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. J. P. Snow, and G. T. Berggren, Jr., Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803. Plant Dis. 72:644. Accepted for publication 2 March 1988. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0644E.
In 1954, Atkins (1) reported that Rhizoctonia foliar blight of soybean
(Glycine max (L.) Merr.) (RFBS) in Louisiana was web blight caused
by Rhizoctonia microsclerotia Matz and characterized by the
production of microsclerotia. In 1977, O'Neill et al (2) concluded that
RFBS in Louisiana was aerial blight caused by R. solani KUhn, which
produces sasakii sclerotia. During the 1987 growing season in southern
Louisiana, rainfall was heavy and frequent and RFBS was severe.
RFBS, characterized by microsclerotia production, was dominant at 11
locations. Fields with only sasakii sclerotia and with both sasakii
sclerotia and microsclerotia were also found. Microsclerotia were
produced when moisture was high, and sasakii sclerotia were produced
after intermittent periods of dry weather. The basidial stage, which had
not been observed since 1954, was found in every field surveyed. Disease
foci having either microsclerotia or hymenia with basidiospores had a
large number of diseased leaves with small circular lesions. These
disease foci produced higher disease incidence and greater disease
spread than foci with neither micro sclerotia nor basidiospores.
Anastomosis tests showed that both types were R. solani AG-l.