If you have plums or cherry trees in your yard...including both fruiting and ornamental...now that the leaves have fallen, get out and take a close look at their branches.
Look for large swollen knots on the branches of these cherry trees.This is a very common disease on plums and cherries called Black Knot.It’s an air-borne disease that spreads in the spring when the spores are injected into the air during rainy periods...and can be spread for miles if the wind conditions are right!
Black Knot affects twigs, branches, and fruit spurs, and over time, they gradually encircle the branch.
In many cases, the smaller branches may die right away, while larger branches last for several years before finally being girdled and die.And in severe cases, like this, the entire tree may gradually be weakened and die if controls are not taken.
So what to do if you discover Black Knot on your cherries or plums?During the winter, or before spring bud break, prune out all infected branches, cutting at least 2-4 inches below each knot.And then destroy those infected pieces.If you find it on larger branches of the tree that cannot be removed, try cutting it away down to healthy wood with a sharp knife, and let the tree seal that wound.Then, use a regular spring fungicidal spraying program of Fungonil or Mancozeb generally from bud break until late spring, especially before rainy periods.
Between catching it early and pruning it out, and the fungicidal sprays, you should be able to get Black Knot under control and save your trees.In a tree like this one, where it has been heavily infected for years, it may be best to remove the tree and replace it.
And I wouldn’t hesitate to replace it with the same tree, now that you know what to look for.