Growth on tree
Based on your photo this looks like black knot, a fungal disease. You may see this on plants in the genus Prunus such as plums, cherries, etc. See our website for photos and more information. http://extension.umd.edu/hgic/black-knot-trees
Prune out the knots as best as possible and destroy the plant material.
If there is a wild cherry growing nearby, and you are able to, you can remove and destroy it. This tree (and others that will be further away) serve as a host for the pathogen. If the tree is badly infected, you may want to consider removal.
Thank you for this invaluable information. Can you tell me the safest way to dispose of the tree parts, etc. that are infected with black knot? Thank you
Dispose of in the trash.