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Diseases on the Maple Tree Bark

By Carole Ellis ; Updated September 21, 2017
Healthy maples may have cracks in the bark, but it holds firmly to the tree.

Maple trees are large, sturdy landscape trees. However, despite their size and relative longevity, these trees do develop some problematic diseases that can shorten their life. Many times these problems develop as diseases on the maple tree bark. The best way to avert problems with maple tree bark diseases is to be aware of the signs and symptoms and deal with the disease as quickly and effectively as possible.

Verticillium Wilt

Verticillium wilt manifests itself at first in ambiguous signs like wilting, yellowing leaves. However, it can be confirmed by bark characteristics. Loose bark at the base of the tree can be indicative of verticillium, and you can confirm this by peeling back the loosened bark to reveal fungal strands or dark, olive-green stained wood. Verticillium wilt usually cannot be controlled once it has reached the bark and roots, and you will likely need to remove the tree to prevent further spread of the disease. However, you can try treating it with fungicides before you opt for plant removal.


Cankers are caused by bacterial and fungal infections. They are hard to spot at first because they start out as slightly discolored depressions in the bark of the tree. However, left to grow unchecked, they create bulging, swollen areas on the bark of the tree that can girdle limbs or even the trunk, causing defoliation, stunted growth and even maple tree death. You can remove cankers using sterile procedures and pruning during cool months when the causal organisms are inactive.

Galls and Burls

Galls and burls are caused by the fungal infection Phomopsis. They are large, tumorous growths that weaken the wood. Branches with galls are more likely to break in the wind. Galls do not appear to spread easily from tree to tree, but they can spread throughout a tree if they are not treated. Prune galls and burls from the tree using sterile technique. Artists often buy galls and burls due to their unique wood formations.