Disease Note.

Occurrence of Powdery Mildew on Prairie Grass (Bromus willdenowii) Cultivar Grasslands Matua. K. T. Leath, U.S. Regional Pasture Research Laboratory, University Park, PA 16802. J. A. Shaffer, and G. A. Jung. U.S. Regional Pasture Research Laboratory, University Park, PA 16802. Plant Dis. 74:828. Accepted for publication 31 July 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0828B.

The prairie grass (Bromus willdenowii Kunth) cultivar Grasslands Matua is grown in New Zealand as a forage crop and is currently being evaluated in Pennsylvania. Powdery mildew developed and became severe on plants of prairie grass grown in Centre County during the summer of 1989, although the disease has not been reported on prairie grass in New Zealand. The mildew pathogen was highly virulent on this host species, and the fungus completely covered some leaf surfaces. Many leaves were killed. Conidia were profuse and typical in size (12.7 X 35.6 µm) and appearance of Blumeria graminis (DC.) E.O. Speer (formerly Erysiphe graminis DC.). Cleistothecia were not observed. The strain of the pathogen that attacks prairie grass does not cause disease on smooth bromegrass (B. inermis Leyss.) (unpublished). This is the first report of powdery mildew on prairie grass.