Latin name: Pseudomonas syringae pv. Syringae
Reason for Concern:
1) Severely infected canes and flower buds that may be killed before they can open reducing yields.
2) Young plants may be killed if lesions are extensive.
3) Atlantic, Burlington, Coville, Chandler, Darrow, N15G (Eberhardt), and Patriot are very susceptible; Elliot, Rancocas, and Weymouth seem more resistant.
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 from a fraction of an inch to the entire length of the stem or girdle stems. Buds in or above the canker area are killed. If the stem is not girdled, buds above the canker grow. Leaves turn orange and wilt if death occurs after buds have leafed out. Severe Botrytis infection can cause similar symptoms.
The bacterium survives and multiplies on the buds, bark and stem surfaces but causes no damage until it enters the stem. Entry is through wounds, natural openings such as leaf scars, and probably through frost- or winter-injured tissues as well. It spreads by wind, rain, insects, propagation wood, and pruning tools. Cold weather and moisture favor the disease.