How to Identify (and Treat) Common Tree Fungus Species

D.P. Taylor
Written by D.P. Taylor
Updated March 30, 2022
A house with lush garden
Photo: Jon Lovette / Stone / Getty Images

Highlights

  • Some tree fungi aren’t harmful, while others are a serious problem. 

  • Careful pruning and prevention can control some fungi, including anthracnose and canker diseases. 

  • Needle blight and tar spots are generally benign types of fungi.

  • Sooty mold doesn't infect the tree itself, but you can prevent it by driving insects away.

  • Powdery mold and root rot cause leaves to yellow, but the latter is more serious than the former.

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Trees are one of the most prized possessions of any homeowner. They add a lot of beauty—and not to mention—value to the property. You’ll naturally want to spring into action if you notice that a fungus has infected a tree. This guide breaks down some of the most common types of tree fungus, how to identify them, and how to treat them.

Yellow Tree Fungus

Yellow tree fungus, also called sulfur fungus, is hard to miss. You've most likely seen it on trees before. It's called the "chicken of the woods" because it’s edible to humans; however, it’s harmful to trees and can cause internal rot.

Identification: This fungus is yellowish to orangish, and it grows up and down the trunk of a tree.

Treatment: You can prevent yellow fungus on trees by being careful with how you prune a tree's branches. Cut the branches at a 45-degree angle to prevent water from collecting and creating a fertile spot for the fungus to grow. Avoid pruning as much as you can, as this fungus thrives on tree wounds.

Anthracnose

Leaves with anthracnose on a tree
Photo: Tunatura / Adobe Stock

Anthracnose, often called leaf blight, mainly infects the leaves of trees, although it can spread to the stems. Unfortunately, there's not much that homeowners can do to stop it.

Identification: Blotches on the leaves are a common sign of anthracnose. It typically infects hardwood trees like sycamores, maples, walnuts, oaks, and dogwoods.

Treatment: The best way to control anthracnose is to prune the infected leaves and branches, a common practice in tree care. You can also try using a fungicide but use it sparingly as fungicides can be harmful to other living things.

Canker Diseases

There are many types of canker diseases, characterized by a fungal pathogen that enters the bark through a wound in the tree. The fungus blocks the tree's vascular system, preventing the circulation of vital nutrients and causing branches to die. Eventually, the entire tree can die in severe cases.

Identification: You can identify cankers as dead areas on the tree, usually on the bark or branches.

Treatment: You should remove branches that have cankers. However, the best way to deal with cankers is to prevent them from happening in the first place. This includes making sure that trees are growing in a suitable space and preventing injury to the tree.

Needle Blight

Needle blights affect pine trees when a fungus grows inside the needle, causing them to die. If left untreated, needle blights can eventually kill the entire tree. However, not all needle blights are serious.

This fungus is easily confused with a white powdery substance on pine trees, which is a separate issue caused by an insect called pine needle scale.

Identification: Needle blight manifests as reddish-brown spots on normally green needles. It eventually causes needles to become completely brown.

Treatment: The best way to treat needle blight is by applying a fungicide in the spring and again in the late spring to early summer.

Tar Spot

Autumn leaves with tar spots on a tree
Photo: Tula L / Adobe Stock

Tar spot primarily affects maple and sycamore trees. While unsightly, they’re not usually dangerous to the tree's overall health.

Identification: Tar spots appear as dark blemishes and spots all over the leaves. These spots usually show up in late spring to early summer.

Treatment: While you can treat tar spot with a copper-based fungicide, it's unnecessary, and fungicides can harm other life forms.

Sooty Mold

This fungus results in a soot-like substance on the leaves. However, sooty mold isn’t a disease because the fungus lives within the honeydew secretion left on leaves by insects like aphids. Therefore, it’s not penetrating the tree. 

Identification: A black ash-like coating covers the leaves, and it may feel sticky to the touch due to the honeydew secretions. 

Treatment: Treating sooty mold is unnecessary because it’s not a threat to the tree. If you want to avoid the unsightly appearance, the best option is to drive away the insects that produce the honeydew. This can be as simple as regularly spraying the leaves with water to knock off insects. 

Shoot Fungus

Shoot fungus is a common fungus found in trees that creates spots on leaves. It's called the shoot fungus because it spreads its spores by shooting them into the air, where they’re carried by the wind and end up sticking everywhere from plants to the sides of houses.

Identification: Shoot fungus appears as dark spots spread over outdoor surfaces, including plants. Once it infects a leaf, it causes dark blotches on the surface.

Treatment: Copper-based fungicides are best for treating this fungus.

Root Rot

Root rot is a serious tree problem caused by overwatering that suffocates the roots and leads to signs of tree death. The rot can spread to healthy roots and kill the tree entirely if left unchecked as the roots decay. However, a fungus that lives in the soil can also cause root rot, and it can be activated by overwatering.

Identification: You'll notice that the tree's leaves turn yellow prematurely. Or, you may see that the tree is not growing well, and its canopy is thinning.

Treatment: Dig around the roots to expose the ball of the roots, and then use a garden hose to rinse it off. Cut away infected roots, and use a fungicide. Contact a tree service company if you’d rather leave this job to a pro.

Powdery Mildew

Powdery mildew is common in humid environments, which is why they’re common in greenhouses. This disease can cause the tree's leaves to turn yellow or brown. In rare cases, this white mold on trees can result in tree death.

Identification: It's easy to spot powdery mildew because it appears as powdery gray spots resembling talcum powder on the leaves. 

Treatment: Sulfur-based fungicides are best for treating powdery mildew. Also, you can prune the tree by removing any infected leaves to keep the disease from spreading.

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