How To Treat Black Fungus On Trees

we're here for you​

Black knot fungus – also known as black knot or black fungus – is one of the most common fungal diseases for cherry and plum trees. If you’re searching for how to treat black fungus for trees, it’s important first to know what you’re dealing with.

Fortunately, identifying and diagnosing black fungus disease is relatively straightforward. 

Black fungus causes trees to get bloated, hard, and develop black knots on their branches and twigs, thus the name “black knots.”

From there, the fungus will develop, enlarge, and spread to the stem of the tree if left unattended.

The fungus then releases its spores, which are easily carried by the wind during the spring.


A newly vulnerable tree receives the spore, where it germinates. The spores that have germinated emit a chemical, causing trees to produce extra plant cells and giving rise to the bloated black knots.

Although the disease primarily affects wild trees, it can also spread to your trees if you don’t properly manage and monitor them.

Symptoms of Black Fungus on Trees

The appearance of black knots on the branches is one of the most obvious symptoms that your trees are dealing with black fungus disease.

Other symptoms include:

  • Branches with infection slanting to one side.
  • Leaves are wilting, turning brown, and dropping off.
  • In severe cases, the whole trunk becomes covered in black knots.
  • When cracked, black knots release a gooey liquid.
  • The wood is decaying.

Does Black Fungus Kill Trees?

Yes, if black fungus disease goes untreated, it will ultimately spread throughout your tree, causing it to die. 

Even if it doesn’t kill the tree, black fungus will seriously affect the tree’s health. In that sense, it can be considered a chronic disease because it restricts a tree’s normal development and growth.

Managing Black Fungus Disease

For those curious about how to treat black fungus, one idea is to follow the “ounce of prevention is worth a pound of cure” school of thought. 

With that, here are a few tips for avoiding and managing black fungus disease.

Fungus-Resistant Trees

Certain trees are less prone to the disease and are resistant to black knot. The easiest method to avoid black knot disease is to choose these resilient trees. 

Maintain Tree Pruning

Pruning can be a good method for managing black fungus disease. This entails removing any branches, twigs, or stems that exhibit disease symptoms. Cut 2-4 inches below the growth in order to completely eliminate all diseased areas.

The cut-off portion still has the potential to infect other trees, so it needs to be burned or properly disposed of. 

To prevent the disease from spreading to other trees, the pruning equipment should also be clean before use.

Use a Fungicide

Using a fungicide is a more efficient means of preventing or eliminating black fungus. But before using a fungicide, though, you must eliminate any current black knots.

Also, it’s best to use fungicide when it’s dry and the temperature outside is above 60 degrees Fahrenheit. From there, follow the fungicide spray’s directions and repeat the application as needed.

Choosing A Fungicide To Treat Black Fungus

The efficacy of fungicides varies. Choosing the right fungicide is very important if you want to stop black fungus disease and cut down on the main infection in your tree.

For the fungicide to be effective against black fungus, it should have active substances such as:

  • Captan
  • Chlorothalonil
  • Lime sulfur
  • Thiophanate-methyl

Mancozeb and Ziram are two fungicides that are highly effective against black fungus in trees.

Speak With One of Our Maryland Tree Experts

Finding out your trees have black knots isn’t always easy, nor is figuring out how to treat black fungus. 

For help effectively fighting and managing this tree illness, consider hiring a professional team to perform the trimming and to apply the fungicides. 

Contact Beautiful Country Tree Service to find out more about starting a treatment plan to protect and save your home’s trees from black fungus.