How to Manage Pests

Pests in Gardens and Landscapes

Pest identification and confirmation—Bacterial blight

Bark infected with Pseudomonas syringae has infected cankers darker than the surrounding, healthy bark and the underlying diseased tissue is reddish brown, moist, and may be sour smelling. A gummy, wet accumulation on the bark adjacent to the canker is characteristic. Cutting into infected bark beyond the margin of cankers may reveal small, brown flecks in the inner bark tissue, especially in apricots and plums. Affected limbs may fail to leaf out in the spring or may produce new growth, which dies soon after temperatures increase in the summer. If trees are killed by bacterial canker, new shoots are frequently produced from the rootstock.

Trees affected by only leaf blight symptoms may not develop cankers and discolored wood. Confirmation of the causal organism would need to be done by a plant pathologist in a laboratory.

Bacterial canker infection
Bacterial canker infection

Red flecks in wood beneath the main canker
Red flecks in wood beneath the main canker

Statewide IPM Program, Agriculture and Natural Resources, University of California
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