Canker
Huge canker (burl) on a cottonwood in Prescott, AZ. Photo with
Logan Garrett for scale.
Cankers on trees and other woody plants can represent serious pathogens and problems or may be quite benign, just like moles, warts and other cosmetic growths on animal and human skin.
Some plant cankers cause leaves to grow smaller and shrivel by affecting the vascular system of the plant. Some cankers cause dead areas on the bark, cause die back, and can kill entire limbs or even entire plants. They are all caused by fungi, bacteria, viruses, parasites like mistletoe and physical damage. Some cankers can girdle roots, shoots or trunks, causing blocked tissue to wilt and die. Cankers ooze liquids sometimes. Blights and canker diebacks look quite similar. Cold-injury symptoms can look like or lead to the development of cankers.
Trees with pathogenic cankers should be treated with the Sick Tree Treatment to eliminate the stress that led to the disease.
Burls are cankers as well. Caused by pathogens or injury stress, the tree reacts by growing a mass of woody tissue covered with bark. These cankers produce beautifully grained wood prized by woodworkers in making smoking pipes, bowls and other decorative creations.
Burls yield a peculiarly interesting wood sought after in woodworking,
and some of them may reach high prices on the wood market. Poaching
of burl specimens and damaging the trees in the process poses a problem
in some areas.
A burl or burr is wood tissue that has grown in a deformed manner, commonly found in the form of a rounded outgrowth on trunks or branches that is filled with flowing growth rings. Burl formation is typically a result of some form of stress caused by injury or viral or fungal infection. They are normally not damaging to the overall health of the plant. Some people think they are ugly – I think they are kinda neat.
Some plant cankers cause leaves to grow smaller and shrivel by affecting the vascular system of the plant.
Some cankers that can actually kill trees include:
 Italian cypress with canker, this appears most commonly if they are planted too deep in the ground. |
- Cytospora canker on pine, spruce, willows, and poplars.
- Phomopsis canker on arborvitae, Douglas-fir, and juniper.
- Nectria canker on maple, oak, and honey locust.
Seiridium cankers can attack most members of the Cupressaceae family. This is a common canker on sick Italian cypress trees, especially those that are planted too deep in the ground. It is said to be incurable, but that’s wrong. Exposing the root flare dramatically and applying the Sick Tree Treatment is the solution.
Hypoxolyn canker is a common disease of certain oaks and other trees, especially after droughts or long rainy seasons. It is not a causal disease. It simply shows up to end the life of extremely sick trees. For example, perfectly healthy trees can loose entire limbs occasionally from this canker after being shaded out or physically injured. No treatment is necessary other than improving the immune system of the tree.
For prevention or cure of problematic cankers, use Tree Trunk Goop on injured spots, improve the environmental conditions and apply the Sick Tree Treatment. Synthetic fungicides do not work on any of these diseases. They kill more of the beneficial microbes than the targeted pathogens.
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