Bacterial canker is caused by two different bacteria: Pseudomonas syringae and Pseudomonas morsprunorum.
These pathogens primarily affect stone fruit trees like sweet and sour cherries, but can also impact plums, peaches, and apricots. The disease manifests through visible cankers (sunken, discolored areas) on branches and trunks, often accompanied by gummosis – the oozing of a gummy substance from the infected sites.
Here's a breakdown of the causal agents and contributing factors:
-
Primary Pathogens:
- Pseudomonas syringae
- Pseudomonas morsprunorum (now often classified as pathovars of Pseudomonas syringae)
-
Disease Development: The disease is most active during cool, wet conditions, typically in early spring. These conditions favor bacterial growth and infection of susceptible plant tissues. The bacteria enter the tree through natural openings like leaf scars or wounds caused by pruning, insect damage, or physical injury.
-
Symptoms: Cankers, gummosis, dieback of twigs and branches, and leaf spots are common indicators of bacterial canker.
-
Contributing Factors:
- Weakened Trees: Trees stressed by poor nutrition, improper planting, pest infestations, or winter injury are more susceptible to bacterial canker.
- Environmental Conditions: Cool, wet weather promotes bacterial spread and infection.
- Wounds: Injuries to the tree provide entry points for the bacteria.
Therefore, management of bacterial canker involves promoting tree health, preventing wounds, and implementing appropriate sanitation practices, such as pruning infected branches during dry weather. In some cases, copper-based bactericides may be used as a preventative measure.
