I noticed these swollen black lumps on the branches of my cherry tree. What is it and what can I do for the tree?
This is called Black Knot – an airborne disease that only affects plants in the Prunus genus – namely cherries and plums, fruiting and ornamental. The infected area eventually girdles the branch and it dies. If you notice one or two of these knots on the branches, prune them out about 6-12 inches below the knot and burn or destroy those pieces. Fungicidal sprays are usually not that effective in helping control it (spring multiple sprays). And if your tree is covered with it, I’d suggest you cut it down.