Black Knot Fungus affects Chokecherry and Mayday in Calgary and has been on the upswing the decade. Many trees have been recently removed due to extent of infection. The disease is transmitted through the air which carries the spores to their new host. Pruning to remove the fungus should be conducted when trees are dormant (Winter).
Our Arborist Matthew Davis was asked for some information on this by CBC Calgary back in 2014, check out the link to the story below
CBC Story on Black Knot Fungus – May 2014
Key Points
- Appear as large “knots” on branches.
- Pruning is the only method of control.
- The occurrence rate of this disease has steadily increased in Calgary over the last decade
- We no longer recommend planting Mayday trees (Prunus Padus) due to it’s susceptibility to this fungus
Tree Damage
- Forms large knots or growths of tissue infected with the fungus.
- These growths eventually choke out the branch and kill it.
Control Measures
- Prune to about 12 inches below point of infection.
- Use proper pruning techniques or hire the services of a certified arborist.
- Avoid planting susceptible species near native tree stands as it can transfer readily.
