Bacterial Canker
(bacterium - Pseudomonas syringae): Elongated cankers develop at the base
of buds and randomly on the trunk and scaffold limbs. Damaged areas are slightly
sunken and somewhat darker in color than the surrounding bark. At both the upper
and lower margins of the canker, narrow brown streaks extend into healthy tissue.
As the trees break dormancy in the spring, gum is formed by the surrounding tissue
and may exert enough pressure to break through the bark and flow. The area beneath
the canker has a soured odor. Individual scaffolds or the entire tree usually
dies shortly after leafing out in the spring. Roots are not affected. Extensive
suckering often occurs at the tree base.
The bacterium is a weak pathogen and causes serious damage only when a tree is in a dormant condition or weakened due to unfavorable growing conditions. Bacterial canker is a component in a disease complex known as Peach Tree Short Life. Trees up to 7 years old, growing on deep sandy soil are most susceptible.
Avoid using high nitrogen fertilizer rates in mid to late summer. Do not encourage late fall growth. Prune when the trees are fully dormant (January and February). High dosage of a copper-containing fungicide at leaf drop has been somewhat successful.
