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Tree Bark Diseases

Most tree bark diseases are characterized by oozing patches and cankers, which are dead sections of bark on the limbs, branches and trunk of infected trees. The disease may not kill the affected tree, but the wounded areas are susceptible to invasion by insects and other diseases. The combined effect of these can cause the tree to decline severely or die.

A laboratory can examine samples of healthy and infected tissues from a tree to determine the causal agent. Local county extension offices can help with taking a sample. There are few effective chemical treatments for tree bark diseases.

Bleeding Cankers

Bleeding cankers are named for the reddish substance that oozes from the cankers. The cankers are caused by the fungus Phytophthora cactorum on deciduous trees. The fungus lives in the soil and enters the tree through wounds at or just above the soil level. The dead wood underneath the bark around the canker is stained red.

Bleeding cankers quickly grow horizontally and vertically. Die-back of foliage and limbs occurs as the canker grows. If the canker girdles the root collar or trunk, the tree will die.

Nectria Galligena Cankers

Nectria galligena cankers are the common type of cankers that occur on deciduous trees. The infection kills the bark while the tree is dormant. The following season, the tree grows healthy callus tissue around the infected area to contain it. During the next dormant season, the infection breaks through the callus and spreads. The canker resembles a target as this cycle continues each season. The bark drops off larger cankers. Reddish fruiting bodies grow around the canker in moist weather. Infected trees should be removed and destroyed.

Pine-Oak Gall Rust

Pine-oak gall rust, also called fusiform rust, is caused by the fungus Cronartium quercuum. Affected pine trees develop long galls, which may be covered in powdery orange spores in the spring. The growth of young trees is stunted by the galls, and the trees usually die. Galls can girdle branches of larger trees, causing them to break at the gall or to die. Galls on branches can grow into the trunk of the tree, resulting in a break at the gall or death of the tree.

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