Cankers On Trees: How Do You Treat Cankers In A Tree

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Image by James Gates

By Susan Patterson, Master Gardener

You may have noticed some unsightly cankerous looking wounds in your tree. What are tree cankers and what causes them, and how do you treat cankers in a tree once you see them? Continue reading to learn more about the types of canker in trees and how to go about preventing tree cankers.

What are Tree Cankers?

Cankers on trees appear as isolated dead areas on the bark, stems, branches or twigs. Cankers may appear as discolored areas or depressed places on the bark.

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A fungus that enters the tree and grows between the bark and the wood killing the bark generally causes cankers. However, cankers can also be caused by damage from weed eaters, lawnmowers, chemicals, insects or environmental conditions.

The canker itself makes the tree highly vulnerable to bacteria, fungus and insects. Young fruit trees have an especially difficult time recovering from cankers. Established shade trees may weaken and become susceptible to wind damage.

The healthier the tree is, the more likely it is to ward off serious damage from a canker disease. Trees that are weakened by temperature, drought, poor nutrition or other present diseases are much more susceptible to canker diseases. Canker diseases are more common with hardwood trees than on conifers.

Type of Cankers in Trees Vary

Depending on the region where you live, different cankers on trees are found. Some of the more common types of canker in trees include:

  • Thyronectria canker is caused by a fungus and is most common on the honey locust tree.
  • Nectria canker tends to attack deciduous shade trees, crabapples and pears.
  • Cytospora canker is found most often in fruit trees, hardwood forest trees and shrubs, as well as over 70 species of conifers.
  • Hypoxylon canker is seen in different species of oak including red and white.

How Do You Treat Cankers in a Tree Effectively?

So how do you treat cankers in a tree? Preventing tree cankers is the best method of protection. It is best to plant native or well-adapted species for your growing region. These tree species will suffer less stress and adapt well to the soil type, sun exposure and overall environmental conditions in your area.

The avoidance of stress is the best and most effective protection against canker diseases. Proper tree care including watering, feeding, mulching and pruning will help to keep trees as healthy as possible.

Once a tree has canker, it is essential to remove as much of the canker fungi as possible from the tree to avoid infection and spread. Prune only during dry weather and make cuts with a sterilized cutting tool at least 4 inches below the edge of the canker on trees.

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