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The Effect of Planting Date on Fall Infections and Epidemics of Powdery Mildew on Winter Wheat. J. A. Frank, Adjunct Associate Professor of Plant Pathology, The Pennsylvania State University, University Park 16802. H. Cole, Jr., and O. E. Hatley. Professor of Plant Pathology, and Professor of Agronomy, The Pennsylvania State University, University Park 16802. Plant Dis. 72:661-664. Accepted for publication 5 February 1988. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1988. DOI: 10.1094/PD-72-0661.

The influence of planting date on fall and spring epidemics of powdery mildew was evaluated during 19821984 on the winter wheat cultivar Hart in field trials in Pennsylvania. The powdery mildew pathogen (Erysiphe graminis f. sp. tritici) infected wheat plants in the fall, but disease symptoms generally were not visible until spring. The incidence of fall infection decreased with later plantings. This fall infection could be prevented with a seed treatment of triadimenol fungicide. The reduction in fall infections led to reductions in disease severity the following spring, although 1 yr there were no differences in disease severities by the end of the spring season. However, the area under the disease progress curve reflected a reduction in the spring epidemic after reduced disease incidence in the fall for all 3 yr. The lowest grain yields were produced from the earliest fall plantings.