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: Pseudomonas bacterial canker on cherry
Photo by: R.S. Byther
Peach : Bacterial canker
(revision date: 3/8/2016)

Bacterial canker is favored by cool, wet weather and is common in western Washington. The bacteria overwinter in cankers, buds and other host tissues. Dark cankered areas on trunks and branches may develop and expand in early spring. The infected tissues may produce gum, although gumming can also be caused by other factors. The cankers often girdle twigs and branches, causing dieback above the lesion. Leaves on girdled twigs often yellow and fall by late summer. Infected buds may be killed or leaf infections may occur as the new growth emerges, resulting in collapse of leaves. Infection can be spread by wind, rain, insects, pruning tools, or by planting or grafting with infected stock. The disease may spread throughout the entire tree with or without visible symptoms (systemic infection).
Management Options

Non-Chemical Management
  • Provide proper culture. Healthy trees are more resistant to disease.
  • Avoid overhead watering.
  • Avoid injury. Do not plant where frost damage is likely.
  • Prune out and destroy infected tissues during dry weather. Make cuts well below visible canker and sterilize tools between cuts. Do not perform disease removal during regular pruning.
  • Burn or cut out cankers on branches or trunks. Cauterizing should be done in the spring prior to bloom. Check cauterized areas for continued bacterial activity 15-20 days later.
  • Remove severely infected trees.
  • Control weeds, which may serve as a source of bacteria.
Select non-chemical management options as your first choice!

Chemical Management

Apply first in October prior to fall rains and again in early January. 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.
  • Bonide Copper Fungicide Spray or Dust RTU [Organic]
    Active ingredient: basic copper sulfate  |  EPA reg no: 4-58
  • Lilly Miller Kop-R-Spray Conc
    Active ingredient: metallic copper  |  EPA reg no: 909-92
  • Monterey Liqui-Cop Copper Fungicidal Garden Spray
    Active ingredient: copper-ammonia complex  |  EPA reg no: 54705-7
  • This list may not include all products registered for this use.

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Caption: Pseudomonas bacterial canker on cherry
Photo by: R.S. Byther
Caption: Incisions showing brown discoloration from bacterial canker
Photo by: R.S. Byther
Caption: Pseudomonas leaf spot
Photo by: R.S. Byther
Caption: Dead bud from Pseudomonas infection
Photo by: R.S. Byther