August 5, 2019
Posted by on
Bacterial canker is a disease that usually kills a tree. In the latest video published on the RealEnglishFruit video channel, Dan Neuteboom explains how he treated a damson tree that was afflicted by bacterial canker, by cutting away the infected parts of the trunk with a chain saw, and painting the wounds with creocoat (a creosote substitute).
It’s easy to see when a tree has bacterial canker: dieback on parts of the tree, and dead areas of bark developing in spring and early summer, with brown gummy liquid oozing out of the trunk. Small round brown spots appear on leaves and later fall out, leaving small holes, known as “shotholes”.
It is an infectious disease, and so it’s best to prune stone fruit trees – plums, greengages, peaches, apricots etc. – only when the tree has leaves and is fully active, so during the summer, because in this period the tree has a degree of resistance to bacterial canker and can heal its wounds. By the end of August, no more pruning should be done on these trees.
Dan’s treatment of this particular tree was performed in July.
The disease is caused by plant-pathogenic bacteria Pseudomonas syringae, which exists in different forms specific to certain tree species. The bacteria land on the leaves where they reside on the surface, and can cause leaf infections in spring and early summer by entering the leaf spores, causing the “shothole” effect. Cankers develop when the bacteria exploit the wound caused by leaf drop or other damage to branches and enter the phloem cells just under the bark – the cells that transport sap rich in sugar and nutrients. The bacteria’s development here blocks the sap tubes causing the death of part or all of the tree.