Influence of Winter Wheat Management Practices on the Severity of Powdery Mildew and Septoria Blotch in Pennsylvania

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Abstract
Effects of row spacing, seeding depth, seeding rate and spring N fertilization level on the severity of powdery mildew (caused by Erysiphe graminis) and Septoria blotch (caused by Leptosphaeria nodorum) on winter wheat were evaluated. Experiments were conducted on 13 farms located in Centre County and Lancaster County, PA [Pennsylvania], during the 1981 and 1982 growing seasons. Management variables tested were 2 planting depths (2 and 4 cm), 2 row spacings (13 and 18 cm), 3 seeding rates (101, 168, and 235 kg/ha), and 4 spring N levels (0, 34, 67 and 101 kg/ha). The management practices evaluated did not consistently interact to influence the severity of either disease, indicating that the effects of any single management practice could be considered individually. As the level of spring N fertilizer was increased, the severity of powdery mildew and Septoria blotch increased significantly. Powdery mildew severity tended to be higher at the wide row spacing and lowest seeding rate. Increasing seeding rate significantly increased Septoria blotch severity in four tests and significantly decreased it in another. Seeding depth did not consistently influence the severity of either disease.