Bacterial Canker
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Bacterial Canker  Bacterial Canker is caused by the bacteria Pseudomonas syringae and morsprunorum. Both pathogens affect sweet cherry, sour cherry, plums and prunes. Disease outbreaks are sporadic and more frequent on sweet cherry than on sour cherry. P. s. syringae is found on peach in the southeastern United States.Susceptible Plants- cherry, peach, plum, prune Symptoms- This bacterial disease attacks most parts of the tree. Cankers on trunks, limbs and branches exude gum during late spring and summer. Leaves on the terminal portions of cankered limbs and branches may wilt and die in summer or early autumn if girdled by a canker. Occasionally, large scaffold limbs are killed. Leaf and fruit infections occur sporadically. Leaf spots are dark brown, circular to angular, and sometimes surrounded with yellow halos. The spots may coalesce to form large patches of dead tissue, especially at margins of leaves, or the centers of the necrotic spots may drop out, resulting in tattered leaves. Infected leaves may abscise during midseason. Lesions on green cherry fruit are brown with a margin of wet or water-soaked tissue. The affected tissues collapse, leaving deep, black depressions in the flesh, with margins becoming yellow to red as lesions and fruit age. On fruit stems, lesions are elliptical and brown with water soaked margins. Infected leaf and flower buds may fail to open in spring, resulting in a condition referred to as "dead bud.' Small cankers often develop at the bases of these buds. Other infected buds open in spring but collapse in early summer, leaving wilted leaves and dried-up fruit. If blossom infection occurs, whole blossom clusters collapse as infection spreads into the fruit-bearing spurs. Outbreaks of bacterial canker are often associated with prolonged periods of cold, frosty, wet weather late in the spring or with severe storms that injure the emerging blossom and leaf tissues. Prevention and Control- The disease is troublesome on some sweet cherry cultivars but not others. Schmidt and Windsor are susceptible and often severely damaged. Hardy Giant is very susceptible-this cultivar should be avoided. Bacterial Canker is a very difficult disease to control. Try to avoid damaging the bark of the trees. Make sure trunks will not rub on any supporting stakes. Take care when cutting surrounding grass. Do not leave rough pruning cuts.
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