Maple: Powdery mildew
Photo by: R.S. Byther
Biology
Powdery mildew of maple is a fungal disease which affects many hardwoods including maple, hazel, birch, and alder.
On maples, a characteristic white, fuzzy or powdery growth appears on the upper or lower surfaces of mature leaves. Sometimes small black structures may be observed in the white areas.
Shoots which develop late in the season may be distorted as a result of the infection.
Management Options
See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.
Non-chemical Management
Select non-chemical management options as your first choice!
- Watch for signs of infection during appropriate weather conditions (dry weather, warm days, and cool nights).
- Pick off infected leaves, when practical, to prevent spread of the disease.
- Gather and destroy fallen leaves.
- Space plantings and prune to provide good air circulation.
Chemical Management
IMPORTANT: Always read and follow label directions when working with pesticides.
For more information on using pesticides visit :
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Apply when the first symptoms appear.
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Homeowners should not make foliar applications to trees over 10 ft tall.
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Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.
Approved Pesticides
If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.
WSU Extension programs and employment are available to all without discrimination.
Evidence of noncompliance may be reported through your local Extension office.