Lots of people in Ottawa ask our arborists about black galls growing on stems and branches, especially during springtime.

What exactly are these funny looking things on our trees? Are they harmful? Do we need to remove them – or remove the whole tree?

Learn how to recognize and eradicate Black Knot fungus, a common disease of plum, cherry, apricot and peach trees. 

Black Knot Fungus: An Overview

Black Knot is a slow developer that takes a season to become visually apparent and produce spores.

Once established, it is easy to identify thanks to its hard and uneven black galls. The trick to controlling the infection is to stop it before it spreads along the tree.

If left untreated, Black Knot may strangle new growth, girdle branches and deteriorate the whole tree. 

Identifying Black Knot Fungus

black knot fungus on a treeDid you know that insects and plants use the galls as an entry to the tree?

By paying close attention to your trees, you can catch the infections as soon as possible and help save them.

When fungi starts to develop, you could prune the affected areas and increase the odds of survival of the tree.  

Untrained eyes often miss the early symptoms of disease, so be sure to hire a tree care expert to inspect your green space before it is too late. 

Susceptible Species 

cherry tree blossoming in ottawa

Some varieties of trees and shrubs are more susceptible to this infection than others, so if you are thinking of planting new ones, try to avoid the species where Black Knot Fungus is prolific.

Tart cherry trees, for example, are known to be less susceptible to the disease than the sweet ones. Also, Japanese plums are said to be less likely to be infected with Black Knot Fungus than the American varieties. 

In addition to cherry and plum trees, this disease can occasionally infect apricot and peach trees.

However, the susceptibility also depends on the climate zone

If you want to pick fruity species that are more resistant to Black Knot Fungus in Ottawa, talk to your local arborists for specific advice. 

Black Knot Fungus in Springtime 

Also called Apiosporina morbosa, this disease becomes progressively more dangerous during each growing season.

Unless effective measures are taken, it can potentially kill a tree.

tree in yard in ottawa

On rainy spring days, the fungus releases spores that are transported by wind currents. If they happen to land on a susceptible tree, the spores germinate and infect it. 

How Is Black Knot Fungus Treated?

Generally, removing the affected part or branch helps save the tree, but only knowledgeable tree care experts can determine the right solution.

Fungicide sprays can also help treat the disease, but without the assistance of an arborist, Black Knot fungus is likely to show up again sooner or later. 

The best solution is the combination of pruning and anti-fungi aerosols. 

Treating Black Knot Fungus in Ottawa

Landscaping can considerably increase property value, so be sure to leave your green space in professional hands. 

At Croft Tree Experts in Ottawa, we provide unmatched expertise in tree services including pruning, hedge and shrub trimming and removing trees and stumps. 

Our Ottawa arborists also offer other services like treatments against pests and diseases, including Black Knot fungus. 

Contact us today to learn more about Black Knot fungus and get a free quote for Ottawa tree services.