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Apple Scab

Venturia inaequalis

Authors: Joseph Zeleznik and Kasia Kinzer

Photo by McGinnis

Figure 1. Infected crabapple leaf, midsummer (Esther McGinnis, NDSU)

Figure 2Photo Bergdahl, ND Forest Service

Figure 2. Crabapple with thinning crown due to premature defoliation (Aaron Bergdahl, N.D. Forest Service)

Figure 3Photo Bergdahl, ND Forest Service

Figure 3. Early infection of crabapple fruits (Aaron Bergdahl, N.D. Forest Service)

 Symptoms

• Early season – Round, velvety, olive-green spots (less than ½ inch) form on leaves and fruit.
• Midsummer – If infection is severe, leaves will turn yellow and fall prematurely.
• Fruit – Spots turn brown and corky through time; fruit may crack and deform.

Management and other important facts

• When possible, plant resistant cultivars. See “Managing Apple Scab in North Dakota Crabapples” (PP1735).
• Raking and removing fallen leaves helps reduce the source of infection for the following season.
• Prune to allow plenty of air movement, and avoid hitting tree leaves with irrigation water.
• Many fungicides are available to prevent this disease, but the spray schedule is intensive.

This website was supported by the U.S. Department of Agriculture’s (USDA) Agricultural Marketing Service through grant 14-SCBGP-ND-0038.
Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the USDA.

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