Effects of Planting Date on Development of Net Blotch Epidemics in Winter Barley in Pennsylvania. L. M. Delserone, Graduate Research Assistant, The Pennsylvania State University, University Park 16802. H. Cole, Jr., Professor of Plant Pathology, The Pennsylvania State University, University Park 16802. Plant Dis. 71:438-441. Accepted for publication 22 October 1986. 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, 1987. DOI: 10.1094/PD-71-0438.

The influence of planting date on fall and spring net blotch epidemics (caused by Pyrenophora teres) was evaluated with the winter barley cultivar Pennrad. Experiments were conducted in Centre County, Pennsylvania, in 1982 and 1983 and in Lancaster County, Pennsylvania, in 1983. The three planting dates evaluated corresponded to the recommended date as well as dates 1 wk earlier and later than recommended for each specific location. Planting date had a significant influence on fall net blotch epidemics, with the greatest and least disease severities observed in the earliest and latest plantings, respectively. When spring environmental conditions were warm and humid, previous differences in disease severities attributable to date were eliminated. With less favorable spring weather, planting date had a significant influence on spring net blotch severities. Planting date also affected yield components, specifically the number of seeds per head and the thousand-kernel weight and the calculated yield. The greatest values for these factors generally were observed for the latest planting. Applications of fungicides during the spring epidemics generally resulted in a significant decrease in disease severity and an increase in one or more yield components. Planting in mid- to late September at either location resulted in the lowest net blotch severities and greatest yields.