WSU Extension

Hortsense

Caption: Pseudomonas bacterial canker
Photo by: R.S. Byther
  
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Plum, Prune (Fresh) : Bacterial canker
(revision date: 5/20/2014)


Biology
Bacterial canker can infect twigs, branches, fruit, or the trunk. Elongate, dark, purplish cankers develop during early spring, often producing bacterial ooze in wet weather. The infected tissues often produce gum, although gumming is also caused by other factors. The cankers can girdle twigs and branches causing dieback. Leaves on girdled twigs typically yellow and fall by late summer. The bacteria typically infect via wounds caused by disease, insect damage, pruning, or frost injury. 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
  • 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.
  • Pseudomonas infection can be very severe on trees with Prunus tomentosa rootstock.
Select non-chemical management options as your first choice!

Chemical Management


None recommended

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Caption: Pseudomonas bacterial canker
Photo by: R.S. Byther
Caption: Pseudomonas bacterial canker on cherry
Photo by: R.S. Byther
Caption: Incisions showing brown discoloration from bacterial canker
Photo by: R.S. Byther