What is Black Knot Fungus, and Will It Kill My Tree?

By: albertaarb - April 8, 2015

Black knot fungus, also called Apriosporina morbosa, has the potential to infect Chokecherry trees, Mayday trees and all other trees within the Prunus family. Although black knot fungus infects strictly Prunus plant species, it is still worth your attention because it can significantly alter the appearance of these trees and if allowed to spread, it can even destroy them.

It is characterized by a collection of lumpy black masses that grow along the branches of trees. This fungal condition is commonly found on cherry trees but it is not limited to only trees that bear cherries.

What Harm Can Black Knot Fungus Do?

While black knot fungus is not always fatal, it can grow and spread throughout your trees. It will harm your trees' health as well as their ornamental value.

When cherry trees are infected with black knot fungus, they can live for a number of years yet they will not look as visually pleasing as your other unaffected trees.

How to Deal With Black Knot Fungus

Put forth the effort and invest the time that is necessary to remove the branches that have been impacted by black knot fungus. Be sure to properly sanitize your pruning tools to limit how much of the fungus is transferred between your plants. Perform a precise pruning and you will boost the trees' aesthetics as well as their vitality.

Prune the infected branches about two to four inches beneath each of the knots. Then dispose of these branches in a landfill. Black knot fungus reproduces in the spring months so avoid pruning them at that time. Only prune the plants when they are dormant. Ideally, you will prune them in the late winter months when the knot-like growths can be easily identified. If you were to wait until the spring to prune the branches, you would find that the fungus is highly active and easily transportable by the spores.

Contact the Professionals

If you have any question about pruning branches that have been infected with black knot fungus, contact Alberta Arborists for the assistance of a certified arborist. Our tree experts are thoroughly educated in a variety of pruning techniques, including the removal of black knot fungus.

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