City launches Combat Black Knot campaign

October 1, 2020

Fort St. John, along with many other areas of British Columbia and Alberta, is experiencing a Black Knot fungus infestation. Black Knot, or Apiosporina morbosa, is a deadly tree fungal disease that attacks predominately ornamental and fruit-bearing plum and cherry trees. The fungus can put the tree’s health at risk, and without removal, can eventually kill the tree.

The fungus is a slow developer, often taking a season to be visually apparent and producing spores, which are then spread to other trees by wind, rain, wildlife, and tools. Once mature, Black Knot presents itself as uneven, hard, dark growths that wrap around branches and twigs.

“We are asking all residents and business owners to inspect all the trees on their properties to help combat the spread of Black Knot,” says Kylah Bryde, Parks Manager with the City of Fort St. John. “It is important to catch the infection early and prune the affected branches when they are dormant, during the late fall or winter.”

Combating Black Knot on your property:

  • Inspect all trees regularly for disease
  • Pruning should be done in the late fall, winter or early spring
  • Remove the infected branches between 6 and 12 inches away from the knot
  • Ensure pruning blades are sharp, clean and disinfected
  • Sanitize your tools between cuts and afterwards to prevent reinfection
  • Discard the infected and removed branches by putting them in a securely tied trash bag for garbage collection or burn them
  • Do not compost infected stems or branches as spores can be produced for up to four months after removal
  • A severely infected tree may be best to be cut down
  • Plant different species that are not prone to the Black Knot disease

The City will be undertaking a community-wide tree pruning campaign in public parks and spaces to combat spread. For more information on Black Knot, visit


Media Contact:
Ryan Harvey
Communications Coordinator
250 794 3313