Black knot cankers in tree

Asked April 21, 2015, 2:44 PM EDT

Not sure what type of tree this is but wondering what the black cankers were and how to fix.

Lincoln County South Dakota trees and shrubs horticulture

1 Response

It appears that this tree has a bad case of Black Knot Disease. It is a fungal disease of stone fruits. I will attach the publication on Black Knot that will help you plus insert the latest from Dr. John Ball on Black Knot, a fungal disease. The tree may be a chokecherry.

I received a picture showing the fungal disease called black knot (Apdiosporina morbosum), also known as dead man’s finger, a very common disease of cherry and plums. These black, coal-like galls that are sometimes covered with a white power can often be found lining the branches and trunks of plums, chokecherries and Mayday trees. A common recommendation is to prune out these galls during the winter months, but this activity has very limited value. First, these blackened galls are the second year of infection. The shoots initially infected last year have only a slight greenish swelling of the tissue. If these shoots are not removed they will grow to form the blacked masses the following year, as you can see it is hard to get ahead of the disease by pruning. The other problem is only some trees are very susceptible to black knot and once they get the disease you can probably expect the tree to become infected again regardless of your pruning efforts. Basal pruning (cutting the tree down) is probably the best approach if you have one that is covered with the knots. Good luck.