Black Knotby mrgadmin on April 22, 2023

In Calgary, black knot fungus affects Mayday and Chokecherry trees. To manage black knot fungus, it’s essential to prune off infected branches 2 to 4 inches below each “knot” and dispose of them in a land fill. The fungus spores overwinter in the masses and reproduce in the spring. Pruning should be conducted when plants are dormant. The best time is during late winter when the abnormal “knotty” growths are clearly visible. The fungus is transported through air which carries the spores to new host. Fungal growth eventually chokes out the branch and kills it.