Whitecourt Food Bank

Black Knot


The Town of Whitecourt is working to control Black Knot within the Town’s parks, boulevards, and public spaces.  Black Knot is highly infectious, and we appreciate the cooperation and support of commercial and residential property owners in helping control its spread.

What is Black Knot?

Black Knot is recognized by clumpy-looking, black masses of abnormal growths on the branches of trees.  This fungal condition infects only Prunus species of plants (i.e. Mayday, Cherry and Plum trees).  These trees are found in yards, boulevards, and parks throughout Whitecourt.

This disease reduces the look of the tree, as infections spread rapidly, and ultimately leads to eventual death of the plant. 

Black Knot is highly infectious and spores can be carried by wind and rain, as well as wildlife.  Removing infected branches/trees will help to control the spread of Black Knot within your property, your neighbour’s property, and the community.

How to Control Black Knot:

Prune out all knot-bearing branches during late fall/winter, or early spring when plants are dormant and knots are easy to see.

  • Remove infected branches to at least 15-20 centimetres (6-8 inches) below knot.  NOTE:  It is preferable to prune an infected branch further back to an appropriate location, such as a healthy collar, rather than leave a stub.

  • As a precaution, cutting blades should be cleaned and disinfected after each pruning cut, if possible, especially if cuts have been made through obviously infected material.

  • For knots on scaffold branches or trunks that can’t be removed, cut away diseased tissue down to good wood and at least 1 centimetre (1/2 inch) beyond the edge of the knot.

  • Failure to remove branches beyond the internal growth will result in re-growth of the fungus.

  • DISEASED WOOD MUST BE DESTROYED IMMEDIATELY (burned, buried, or removed from site and disposed of at the landfill). Diseased knots can produce and release spores for up to 4 months after removal.

  • When disposing of infected wood at the Whitecourt Regional Landfill, please inform staff upon entry so that you can be directed to the proper disposal area.

  • Consider hiring a trained professional for pruning activities.




Do you have questions about black knot? Contact the Town of Whitecourt at 780-778-2273.