What is it?

Black knot is a fungus that can affect Mayday and Cherry trees. The spores are spread by wind, rain, insects and birds. Corky, black, spindle-shaped swellings found on the branches and twigs are the symptoms of this disease.

What can I do?

Remove branches 10 cm down from the point of infection. Sterilize cutting tools with household bleach after each cut and dispose of all infected branches in sealed garbage bags along with household garbage - not yard waste. You may remove branches from Chokecherry or Mayday trees at any time of the year however it is easier to identify and prune out infection in the fall through to the spring. There are also many excellent certified arborists in Central Alberta that will help you properly care for your tree. Always employ proper pruning practice to maintain healthy trees.

For more information, please view the Black Knot (pdf) pages from our Integrated Pest Management Manual or Black Knot Information Sheet (pdf)