The fungus Eutypella kills the growing layer of cells under the bark, the cambium, and causes a distinct bulge of callus to develop around the infected area of red, sugar, silver, Norway, and other Maples. Dead bark remains attached to the canker which may be on one side of the trunk or completely girdle the tree. Often, there is a dead branch stub in the center of the swollen, cankered area.

Maples, especially young trees, in ornamental plantings are susceptible to this fungus. In most cases, between 2% and 10% of the trees may be affected. Not only is the visual value of the tree reduced by the presence of the swollen, callused trunk, the tree is very susceptible to attack by wood decay fungi and then to wind breakage. The infected tree becomes a hazard to people and property in the vicinity. It is very important to inspect your tree for Eutypella Canker.

The canker is most often seen between 3 and 10 feet above the ground. This perennial canker enlarges year after year and may become up to 3 feet long. The tree produces callus during the growing season in response to the presence of the fungus. The fungus kills this callus and invades more cambium and bark during the tree’s dormant season. Occasionally the fungus dies in the tree and the tree produces a large roll of callus along the canker’s edge.

The fungus produces spores, sexually in the centers of old cankers that are more than 5 years old. These spores are forcibly discharged during mild, moist weather and are carried by the wind from tree to tree.


Symptoms and Signs

  • A large roughened area of bark, sunken in the center with heavy callus around the margin, is observed on the branch or main trunk. Usually there is a branch stub in the center of the canker and the canker is within 10 to 12 feet of the ground.
  • When bark is removed from the upper and lower ends of the canker at the junction between the diseased and healthy wood, a light tan to cream colored mass of fungus is observed.
  • Black fungal fruiting structures protrude from the bark near the centers of 5 year old or older cankers.


  • Remove trees with cankers on the main trunk
  • Remove all cankered branches, cutting 4-6 inches below the canker. Be sure to do the pruning when the weather is dry.
  • If the tree is highly valuable, use a sharp chisel to remove the entire cankered wood and fungal mat. Also, remove 1-1.5″ of healthy wood that is surrounding the fungal area.
  • Remove the lower limbs, those that are less than 1 inch in diameter.
  • When a limb breaks, remove the remains with a clean cut close to the branch collar without damaging the collar. SEE BELOW

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