There have been reports of Black Knot in trees in and around Strathmore lately. Black Knot is an infectious fungus that affects trees such as Mayday, Schubert, Chokecherry, Plum, and Cherry trees.  

Black Knots' most distinguishing symptom is the characteristic black tar-like symptoms that develop on the branches of the infected plant. 

The infection can spread rapidly via wind and rain. If Black Knot is not controlled, it can lead to a high level of infection in your tree and in neighboring trees of the same family and may lead to the eventual death of the tree. 

The Operations Manager for the Town of Strathmore Donna McCallum explains the most effective way to control Black Knot is to prune all knot bearing branches.  

“Prune your tree in late fall, winter or very early spring when the tree and the knots are dormant. Avoid pruning your tree when the tree has buds or is in full leaf. Pruning during the active growing season will result in spreading the fungus throughout your tree and neighboring trees.”  

McCallum added that if you decide to prune out the Black Knot yourself, please keep in mind that it is important to remove the infected branches using proper pruning practices. 

“It is important not to cut into the branch bark ridge or the branch collar. Cutting in this area will make it difficult for the tree to “heal” the wound and can leave your tree susceptible to further infections or infestations from insects.” 

For further assistance with pruning black knot out of your tree or shrub Look into hiring a Certified Arborist. Visit for a list of Certified Arborists within the Strathmore area.

Prune treeProper pruning procedures.

For more information about Black Knot, visit

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