Caption: Pseudomonas bacterial canker on cherry
Photo by: R.S. Byther
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Common Diseases : Pseudomonas bacterial canker
(revision date: 4/30/2013)
Biology
Pseudomonas bacteria remain alive in old cankers, in buds, and on plant surfaces of infected trees and on many kinds of plants, including weeds and grasses. Bacteria may be systemic within the tree. The bacteria can be spread by splashing, windblown rain, irrigation water, insects, and infected bud wood and nursery stock. Infections occur during wet periods, especially during cool, wet weather. The bacteria enter the plant through natural openings and wounds. The most apparent symptoms are branch or trunk cankers, gumming, and branch dieback. Numerous woody ornamentals and fruit producing plants are susceptible: Cherry, plum, Asian pear, peach, blueberry, raspberry, etc. Cankers may or may not appear sunken, but significant gumming is usually associated with canker margins on Prunus species. However, gumming is not specific to bacterial canker. Other factors, such as injury, improper growing conditions and other disease can cause gumming, too. Cankers develop in the winter and early spring. When tree growth begins in spring, the canker stops expanding and the wound begins to close. At times, however, the canker may have girdled the branch or trunk.
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