Gardening - Fruit: Pests & Diseases
Black knot is common disease of plum, prune and cherry. Both cultivated and wild species of these plants are susceptible to this disease. Trees severely infected with black knot become an eyesore and are almost worthless as an ornamental plant after several years. This is particularly true in small home orchards or yards, where no control measures are attempted.
"SP277-X-Black Knot of Plum and Cherry," The University of Tennessee Agricultural Extension Service, SP277X-500-5/01(Rev) E12-4615-00-037-01, http://trace.tennessee.edu/utk_agexgard/11