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Disease Note

Downy Mildew (Sclerophthora macrospora) of Wheat, Barley, and Oats in North Dakota. V. L. Jons, Crop Production Service, Moorhead, MN 56560. B. Nelson and M. McMullen, Department of Plant Pathology, North Dakota State University, Fargo 58105. Plant Dis. 70:892. Accepted for publication 28 April 1986. Copyright 1986 The American Phytopathological Society. DOI: 10.1094/PD-70-892d.

In June 1985, durum wheat (Triticum durum Desf. 'Lloyd') and barley (Hordeum vulgare L. emend. Bowden 'Azure') plants (2050% incidence) showing stunting, leathery leaves, excessive tillering, and deformed heads were observed in wet areas of two fields near Casselton, North Dakota. Similar symptoms were observed in wet areas in oat (Avena sativa L. 'Porter,' 'Steele,' 'Dumont,' and many experimental lines) breeding nurseries in Fargo and Prosper. These symptoms were initially attributed to phenoxy herbicide injury, but microscopic examination of leaf tissue of each crop showed abundant oospores of Sclerophthora macrospora (Sacc.) Thirum., Shaw & Naras. (1,2). This is the first report of downy mildew on these important cereals in North Dakota. Wet, cool conditions during 1985 provided a favorable environment for disease development. Because of the similarity of downy mildew symptoms to those of herbicide injury in small grains, this fungal disease most likely was misidentified as herbicide damage in past years.