Apple & Crabapple Diseases Powdery Mildew

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This disease is caused by the fungi Sphaerotheca species or Podosphaera species and is most prevalent during dry, hot periods. The fungus causes gray-white powdery patches on leaves and new shoots. New growth is often stunted, curled and distorted. Fruit may turn russet-colored and develop poorly.

Prevention & Treatment: Prune out branches or infected twigs early in the season. If disease is severe enough to warrant chemical control, choose one of the following fungicides for use on apple trees and crabapple trees: thiophanate-methyl, basic copper sulfate, lime sulfur, wettable sulfur (minimum 80 percent), propiconazole (do not eat fruit) or triadimefon. Some of these chemicals can injure the tree if applied at the wrong time. Apply all chemicals according to directions on the label.

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