Gardeners and nurseries often grow cherry trees as ornamental trees and for their fruit. Fungal diseases can affect the health of the tree, as well as the fruit it bears.
According to North Dakota State University, black knot is a fungal disease occurring in chokecherry and sour cherry trees and is caused by the fungus Dibotryon morbosum, which causes knots to develop on tree stems. Another fungal disease of cherry trees is plum pockets, which endanger fruit development. Plum pockets commonly occur on chokecherry, wild black cherry and Nanking cherry trees.
Symptoms of black knot disease includes knots on branches or tree trunks that eventually girdle the entire tree. Knots often grow for several years before girdling the tree trunk or branches. Plum pockets cause fruit on trees to become hollow and enlarged. Shoots are distorted and leaves curl. A witches broom is common among cherry trees with this disease, especially on sour cherry trees.
Control of fungal diseases such as black knot includes pruning and fungicides to kill the causative fungus. Lime sulfur is an effective treatment for plum pockets in cherry trees, but you must apply it in the springtime. Consult your local extension office for advice on treatments.
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