Interaction of Planting Date and Powdery Mildew on Pea Plant Performance1

Abstract

Abstract In weekly plantings of peas, Pisum sativum L., later plantings emerged faster and required less time to reach bloom and harvest stages than early plantings. Later plantings, however, required slightly more heat unit accumulation to reach the harvest stage jthan early plantings. Powdery mildew (caused by Erysiphe polygoni D.C.) was severe in later planted plots 1 year. Unprotected plots yielded only 44 to 71% as much as protected plots. From those planting dates where powdery mildew affected yields, fungicide-sprayed plots had lower tenderometer values at harvest than unsprayed plots. Yields of an early cultivar showed no particular trend with planting date except for drastic reductions in unprotected late planted plots 1 year. Yields of the late cultivar tended to decrease with delayed planting, with especially sharp reductions in unprotected late planted plots 1 year.