WSU Extension


Ornamental Cherry : Bacterial canker
(revision date: 5/19/2015)

Bacterial canker can be found on any part of the tree. The disease causes cankers and dieback of twigs and branches. A typical branch canker is elongate and enlarges during the dormant season from around the base of an infected twig. It may leak sap (gumming) at the edges of the canker and may show brown or black streaking in the wood when cuts are made at the top or bottom of the canker. Cankers can girdle limbs or trunks. Bacterial canker can kill buds in winter and blossoms in the spring, and can also cause dead spots on leaves. In combination with frost the disease can cause serious damage to trees.
Management Options

Non-Chemical Management
  • Locate trees in areas least likely to be affected by frost.
  • Prune and destroy infected branches before wet weather begins in the fall. Make pruning cuts well below infected area and disinfect tools between cuts.
  • Do normal pruning in January or February.
  • Remove severely infected trees.
  • Cauterizing (burning out) cankers with a propane torch has had some success.
Select non-chemical management options as your first choice!

Chemical Management

Apply fixed copper before fall rains, during leaf fall and late dormant just before buds open. 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
  • Bonide Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • 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
Caption: Pseudomonas bacterial canker
Photo by: R.S. Byther