Diagnose Tree Fungus

Diagnose tree fungus early to prevent damage.

Fungal infections in trees are caused by fungi spores that attach themselves to the tree and begin to grow. Fungal infections most often occur at areas of injury to the tree, such as broken branches, gouges or, sometimes, areas of pruning. Fungal infections can occur on the leaves of the tree as well as the trunk and branches. Diagnosing tree fungus early is critical to controlling it. If not treated quickly, the fungus will spread and can eventually kill the tree. Does this Spark an idea?


1. Examine the woody sections of tree branches and look for dark brown or black spots on it. The dark spots are sometimes moist to the touch if the fungal infection is new. If these spots are present, it indicates the presence of a condition called sooty canker. This condition is also characterized by bark that falls off of the tree to reveal black spots on the underlying wood.

2. Examine the tops and bottoms of the leaves of the tree and look for tiny black fungal spots which indicate the presence of mildew on the tree. These dots look just like mildew that occurs inside a home or on wet fabric, so they are easy to identify.

3. Look at the tops of the tree leaves for a fine, white, powdery substance that looks like powdered sugar. This is a fungal condition called powdery mildew and occurs during spring or fall when the temperatures are between 60 and 80 degrees Fahrenheit.

4. Look at the main trunk of the tree for signs of a fungal infection called canker. Canker spots frequently look like bumps in the tree bark because the tree attempts to heal itself by growing over the canker. The bark is usually split and the black colored canker wood is visible underneath it.