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Bacterial
canker
Pseudomonas
syringae (bacterium)
Annemiek Schilder,
MSU Plant Pathology
Bill
Cline, NCSU Plant
Pathology |
| Bacterial canker is a
minor stem disease that occurs mainly in western North America. |
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Symptoms.
Symptoms first appear in January or early February
as water-soaking on 1-year-old stems. The lesions rapidly
develop into reddish brown to black, irregularly shaped cankers
with definite margins. Cankers can extend the entire length
of the stem or girdle stems. Buds in or above the canker area
are killed. Shoot tip dieback is the most common symptom on
young plants in nurseries or cuttings in propagation beds. |
| Stems killed by bacterial canker in a young blueberry field. |
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Disease
cycle.
The bacteria survive on the buds and bark and enter the plant through
wounds caused by frost or pruning. Only 1-year-old stems are attacked.
The bacteria can be spread by wind, rain, insects, propagation wood,
and pruning tools. Cold weather and moisture favor the disease.
Management.
Prune out diseased stems before the onset of fall rains; avoid
late-summer nitrogen applications; apply copper in fall and spring;
avoid wounding; protect from freeze injury; sterilize pruning
tools.
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