Black knot can occur on both sweet and sour cherry, Damson, American, European, and Japanese varieties of cultivated plums and prunes as well as wild cherries and plums. The disease is common throughout much of North Carolina occurring on many wild plum and cherry trees. These serve as an annual source of infection for cultivated varieties.
Black knot occurs on the woody parts of the tree such as twigs, limbs and sometimes the trunk.
The knot is unsightly and often becomes infested by borer-type insects. The disease may become very destructive causing death of effected twigs and limbs, and occasionally entire trees. There is great variation in level of susceptibility in wild cherry. However, the first symptoms are small, light brown swellings usually located at the base of the leaf petiole or on the fruit spur. These appear usually during the summer and first year after infection.