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There are many different types of cankers that can attack trees and shrubs. Cankers can be caused by both fungal and bacterial infections, but the control method is the same for both types of infection.
On the tree, cankers appear as dark, sunken areas on the trunk and major branches. A canker is often caused by a fungal or bacterial infection within the tree’s vascular system, bursting out beyond the bark. When a canker appears, the bark around it often dies and breaks off, exposing the tree’s fragile vascular system to environmental stress and degradation.
Often the canker will produce a sticky sap substance that oozes from the canker down the trunk or branch. Often the sticky sap attracts insects such as ants and wasps, but they are just a symptom of the canker not the cause. Cankers are caused by a fungus or bacteria that enters bark that has been injured by sunscald, cold injury, boring insect damage, improper pruning wounds or physical injury to the tree.
As the infection spreads it cuts off the tree’s vascular system and causes die-back in the region of the canker. If the canker spreads all the way around the trunk or a major branch, it will fully disrupt the vascular system and cause the branch or the whole tree to die. In most cases a tree is not killed by a canker, but if left untreated it substantially weakens the tree leaving it vulnerable to another disease or insect attack.
During dry weather prune and remove infected branches. Limbs should be pruned 6 to 10 inches beyond the canker symptoms. If the canker is located on the trunk, surgical removal of the canker may save the tree. Using a very sharp knife and a chisel like tool, remove all discolored bark and wood from the canker site. After each cut it is important to sterilize the cutting tools with a mixture of 1 part bleach and 2 parts water, otherwise the bacterial or fungal infection will be transferred to the healthy wood.
Spray the canker area with Agri-Fos & Pentra-Bark Disease Treatment. Ensure that the entire area is well treated. The Pentra-Bark additive helps the fungicide penetrate into the tree’s vascular system. Repeat the spray program every 21 to 30 days for 3 sprayings.
To help the tree recover from a canker infection, ensure the tree is properly fertilized, using a TreeHelp Annual Care Kit.