WSU Extension


Bacterial canker 
Brown rot 
Crown gall 
Cytospora canker 
Leaf curl 
Powdery mildew 
Shothole (Coryneum blight) 
Brown marmorated stink bug 
European red mite 
Peach twig borer 
Peachtree borer 
Spotted wing Drosophila (SWD) 

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Caption: Powdery mildew on peach
Photo by: R.S. Byther
Peach : Powdery mildew
(revision date: 1/22/2016)

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

Non-Chemical Management
  • 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.
Select non-chemical management options as your first choice!

Chemical Management

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 degrees F, above 90 degrees 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.

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 reg no: 54705-10
  • Bonide Infuse Systemic Disease Control
    Active ingredient: propiconazole  |  EPA reg no: 100-773-4
  • Bonide Sulfur Plant Fungicide Micronized Spray or Dust RTU [Organic]
    Active ingredient: sulfur  |  EPA reg no: 4-62
  • Hi-Yield Snake Eyes Dusting Wettable Sulfur
    Active ingredient: sulfur  |  EPA reg no: 7401-188-34911
  • Lilly Miller Sulfur Dust Fungicide/Insecticide Dust or Spray
    Active ingredient: sulfur  |  EPA reg no: 802-16
  • Monterey Horticultural Oil [Organic]
    Active ingredient: mineral oil/pet distillate light  |  EPA reg no: 48813-1-54705
  • Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
    Active ingredient: myclobutanil  |  EPA reg no: 9688-123-8845
  • This list may not include all products registered for this use.

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Caption: Powdery mildew on peach
Photo by: R.S. Byther