Peach: Powdery mildew

Biology

Powdery mildew of peach attacks leaves, young shoots, and fruit. This fungal disease produces a characteristic white, powdery coating on the surface of affected leaves. Older leaves may show patchy areas of fungal growth, while shoots may become covered with the fungus. Diseased tissues are often deformed and stunted. Fruits first develop white circular spots, which may enlarge and coalesce to cover the entire fruit. Young fruit may be somewhat deformed, while older fruit may show scabby or dead areas. At this stage, the white fungal growth may not be visible. The fungus can overwinter on twigs and in infected buds. Powdery mildew is favored by high humidity, warm days, and cool nights.

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 more resistant varieties such as ‘Angelis’, ‘Halford’, ‘Johnson’, ‘Stuart’, and ‘Walton’. These varieties may not be suitable for western Washington.
• Plant in full sun.
• Space trees and prune to provide good air circulation.
• Carefully prune out severely affected shoots. Remove infected fruit.
• Minimize irrigation around trees as much as possible.
• Remove nearby susceptible rose bushes.

Chemical Management

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

• Apply at first sign of disease.
• Repeat at one to two-week intervals, until conditions are no longer favorable for disease development.
• Do not use oils within 14 to 30 days of a sulfur application.
• Do not use oils below 50° F, above 90° F, or when plants are under heat or moisture stress.
• Do not use when foliage is wet, as good coverage is essential.
• 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.

• Bi-Carb Old-Fashioned Fungicide [Organic]
  Active ingredient: potassium bicarbonate [EPA registration number: 54705-10]
• Bonide Infuse Systemic Disease Control
  Active ingredient: propiconazole [EPA registration number: 100-773-4]
• Bonide Sulfur Plant Fungicide Micronized Spray or Dust RTU [Organic]
  Active ingredient: sulfur [EPA registration number: 4-62]
• Hi-Yield Snake Eyes Dusting Wettable Sulfur
  Active ingredient: sulfur [EPA registration number: 7401-188-34911]
• Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
  Active ingredient: sulfur [EPA registration number: 802-16]
• Monterey Horticultural Oil [Organic]
  Active ingredient: mineral oil/pet distillate light [EPA registration number: 48813-1-54705]
• Spectracide IMMUNOX Multi-Purpose Fungicide Spray Concentrate
  Active ingredient: myclobutanil [EPA registration number: 9688-123-8845]
• This list may not include all products registered for this use.