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 (systemic infection) with or without visible symptoms.

Management Options

Non-Chemical Management

Mazzard rootstock F12-1 and cultivars 'Corum', 'Sam', and 'Sue' are disease-resistant.
Provide proper culture.
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 frequently. Do not remove cankers at the same time as 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

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

Focus on cultural management first. If you supplement with chemical control, make one application in October during leaf fall prior to fall rains. Then make a second application in early January. Products containing copper may have limited efficacy due to resistance. 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 Liquid Copper Fungicide Conc/Organic Gardening
Active ingredient: copper octanoate | EPA reg no: 67702-2-4
Monterey Liqui-Cop Copper Fungicidal Garden Spray
Active ingredient: copper-ammonia complex | EPA reg no: 54705-7
Soap-Shield Flowable Liquid Copper Fungicide [Organic]
Active ingredient: copper octanoate | EPA reg no: 67702-2-56872
This list may not include all products registered for this use.

Images

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Caption: Pseudomonas bacterial canker on cherry Photo by: R.S. Byther
Caption: Pseudomonas bacterial canker 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

WSU Extension

Hortsense