Crabapple: Powdery mildew

categories: Crabapple Crabapple Diseases Ornamental trees Ornamentals

revision date: 2024-06-05 10:40

Powdery mildew on apple leaves against a black background.
Powdery mildew on apple leaves
Photo by: R.S. Byther


Powdery mildew of crabapple is typically seen on the foliage, but may also occur on twigs, blossoms, and fruit. Characteristic patches of white, powdery fungus develop on the leaves and terminal shoots. Infected young leaves often become deformed and curled. Infected shoot tips may be deformed or die back. Small black fungal fruiting bodies may develop in the white areas. Symptoms of fruit infection include white powdery growth and russeting (development of brown or rust-colored, corky patches on the fruit). The fungus may overwinter in infected buds.

Management Options

Use Integrated Pest Management (IPM) for successful plant problem management.

Non-chemical Management

Select non-chemical management options as your first choice!

  • Plant trees in full sun.
  • Plant resistant varieties. Crabapples with good to excellent powdery mildew and scab resistance include ‘Christmas Holly’, ‘Evereste’, ‘Golden Raindrops’, M. baccata v. jackii, M. x zumi ‘calocarpa’, ‘Molten Lava’, ‘Prairifire’, ‘Professor Sprenger’, ‘Sentinel’, ‘Sugar Tyme’, ‘White Angel’, ‘Winter Gem’.
  • Prune and destroy severely infected twigs and branches to reduce spread of disease.
  • Clean up and destroy fallen leaves from beneath infected trees. Powdery mildew can overwinter in infected leaf debris.

Chemical Management

IMPORTANT: Visit Home and Garden Fact Sheets for more information on using pesticides.

  • Pesticide recommendations are for flowering (non-edible) crabapples.
  • Apply fungicides when flower buds begin to expand, when flower buds are exposed, and when flower blossoms are present.
  • Necrotic foliage may result if oil products are applied within 10 to 14 days of a sulfur application.
  • Do not use oils below 50 degrees F., above 90 degrees F. or when plants are under heat or moisture stress.
  • Homeowners should not make foliar applications to trees over 10 ft tall.
  • Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

Approved Pesticides

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.

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