Spring is nearing and I wanted to share a link to MSU extension that I came across recently. It pertains to Black Knot on ornamental trees. Species impacted are predominently in the Prunus family. Examples include Flowering Plum, Canada Red Chokecherry, Flowering Almond, and fruit producing forms of the Prunus family. If you have any of these varieties, inspect your trees and follow the management strategies suggested in this link. Much of this information relevent to trees in nursery production, but the management strategies and warning signs are applicable to anyone with these types of trees.
Hopefully you are not experiencing these problems, but it is always better to be proactive in the event that you do see some of the warning signs.