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Disease Note

First Report of Sclerotium rolfsii Infection of Poa annua in Illinois. R. T. Kane, Department of Plant Pathology, University of Illinois, Urbana 61801. H. T. Wilkinson, Department of Plant Pathology, University of Illinois, Urbana 61801. Plant Dis. 76:538. Accepted for publication 15 January 1992. Copyright 1992 The American Phytopathological Society. DOI: 10.1094/PD-76-0538D.

A spreading foliar disease of Poa annua L. was noticed on northern Illinois golf course putting greens during August 1988 and 1991. Both years were notably hotter and drier than normal. Rapidly growing mycelia were found in the canopy and in thatch of advancing margins of circular rings 15-25 cm in diameter. Individual plants wilted and turned yellow. Most plants recovered as colonization expanded, although some necrotic rings were later observed on greens. Bentgrass plants in the sward were affected less severely. Standard techniques were used to isolate Sclerotium rolfsii Sacco directly as aerial mycelium and from diseased leaf tissue. Brown sclerotia and clamp connections were observed only in vitro in 7-day-old cultures. Identification of the pathogen was confirmed by L. L. Burpee (University of Georgia). S. rolfsii causes a serious disease of P. annua in California (1). This is the first report of southern blight of P. annua in Illinois.

Reference: (1) Z. K. Punja and R. G. Grogan. Plant Dis. 67:875, 1983.