If you have stone fruit trees (plums, peaches, apricots, etc.) then you know the tree are susceptible to certain diseases. Canker is a common issue and learning how to deal with sunken canker on plum trees will enable you to save an infected tree.
Sunken canker is an outward sign that something is wrong inside of the tree and unless the problem is corrected the plum tree will die. The cause of sunken canker are many but the treatments are few and must be administered quickly to save the plum tree.
What Does Sunken Canker Look Like?
It’s a sunken, discolored area on the plum tree trunk or branch. These sunken spots usually appear in early spring and often have foul-smelling sap oozing from them.
The cankers can be round or oblong, and sometimes there will be no visible sap oozing from them.
The shape and whether or not sap is oozing from the sunken canker will provide the clues needed for proper treatment.
Round, Oozing Sunken Canker
Bacterial canker produces round, oozing lesions on plums trees that have been stressed. The stress can be from transplanting, spring weather that is too wet, dry, or hot. These round cankers can also be at the point where the plum tree was pruned. The primary cause will be several overly wet and warm springs in a row that create the perfect environment for bacteria to flourish.
Oblong and Dry
This type of sunken canker on a plum tree are usually caused by injury. Improper pruning, tree grafting, or hitting the tree trunk with a mower or weed whacker are the common culprits.
The injury to the tree allows bacteria to enter where the bark has been compromised. Wet, warm weather conditions promote the growth of the bacteria and the outward sign of sunken canker will appear, along with pitted, ridged bark.
Smelly sap can begin to ooze from these sunken cankers if the plum tree is not treated.
Leaf Appearance
Plums trees that are affected with sunken canker will also develop ‘shot holes’ on the leaves. The leaves will eventually turn yellow and fall off, permitting too much sunlight to directly hit the developing plums and cause the plums to be sunburned.
Treatment
Sharpen pruning shears and prepare a bucket of disinfectant that is 1-part liquid bleach and 9-parts water. Prune off all infected branches, dipping the shear blades into the disinfectatnt between each cut to prevent spreading the canker.
Discard pruned branches away from all trees and rake the soil clean under when finished.
Spray plum tree with a copper fungicide or broad-spectrum fungicide after pruning.
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