WSU Extension


Birch leafminer 
Bronze birch borer 
Oystershell scale 

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Caption: Birch Botryosphaeria canker
Photo by: R.S. Byther
Birch : Canker
(revision date: 4/28/2014)

Several fungal pathogens can cause canker disease of twigs and branches. Young cankers appear darker and slightly more sunken than adjacent healthy bark. As they grow, they kill living woody tissue, and may cause bark along its edges to crack and fall off. Once a canker girdles a branch or trunk, the portion above the canker dies. Trees with cankers are usually stressed by drought, defoliation, wind damage, nutrient imbalance, flooding, soil disturbance, snow and ice damage, injuries from birds and insects, and other severe conditions. Symptoms may include upper branch dieback, disfigured branches, and target-shaped areas with concentric rings of dead bark on trunks. Cankers generally cause only minor dieback, but may be indicative of poor health.
Management Options

Non-Chemical Management
  • Prune affected branches back to healthy wood.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Birch Botryosphaeria canker
Photo by: R.S. Byther