AIRCRAFT-APPLIED SULFUR FOR CONTROL OF POWDERY MILDEW (ERYSIPHE-CICHORACEARUM) ON POTATO IN WASHINGTON-STATE

Aircraft-applied dust and liquid sulfur sprays were evaluated for control of powdery mildew (Erysiphe cichmacearumDC), on rill irrigated potatoes (cv. Russet Burbank). Either form of sulfur applied weekly or biweekly usually controlled E. chichoracearum through September, but not in October. Significant yield increases were obtained in only two of five trials. The small differences in disease severity between weekly and biweekly applications of sulfur were not significant. Sulfur gave very little control if applied after infection was established. Applications of liquid sulfur, the formulation less likely to cause environmental problems, should be started at the first trace of stipples on stems and continued biweekly throughout the season. © 1990, Springer. All rights reserved.