Black knot disease

Asked August 2, 2016, 4:57 PM EDT

I have 3 choke cherry trees that have black knot disease and I have been told there is nothing to be done to save them. I have been told by an arbornist that the branches can be pruned back but to do in the spring. Just wondering what would be the problem if I pruned in late fall. Love these trees and would really like to save them. Thank you for your anticipated help.

Lake County Indiana trees and shrubs fruit trees chokecherry trees

1 Response

The prospects for saving the trees depends on how extensive the black knot infestation is. If the knots are at the base of the trees, then the crown area is likely infected as well--in this case it will be very difficult to eliminate the disease. If the knots are out on the limbs, then I suggest you prune out the visible knots plus another 6 inches of apparently healthy wood--burn or bury the limbs. Choke cherry are pretty resilient trees. I suggest that you prune now rather than wait for fall when the impact on the tree will be greater.
You will need to inspect the trees at least 3 times a year and prune out any new knots as they appear. Spraying for black knot next year will be necessary to help get the disease under control. There are hidden infections from this season (2016) that will show up next spring--sprays next spring will not control these, but will help prevent new infections that would show up in late 2017.
See the following for further tips.
http://msue.anr.msu.edu/news/controlling_black_knot_in_michigan