6 Common Maple Tree Problems
6 Common Maple Tree Pests and Problems
When I worked as an editor of a gardening channel, people often asked me how to identify and address common maple tree pests and diseases. Whether you don't have any idea what anthracnose is or you don't know how to identify lichen, you'll find a few common issues below that may help you pinpoint the problem.
Six common issues you may come across are:
- Maple tree tar spot
- Sooty mold
- Verticillium wilt
- Root rot
Maple Tree Tar Spot
The maple tree tar spot is fairly easy to identify. It's caused by a fungal pathogen in the genus Rhytisma. While this affects maple trees in general, it especially targets the Norway Maple, Silver Maple and Sugar Maple. Tar spot will not kill your trees, but it's unsightly and can cause them to drop their leaves before the fall season.
The spots first appear as small yellow spots in June. Then, they progress to the black spots on the leaves you see above. Their size ranges from one-eighth of an inch to an inch or more in diameter on the Norway Maple. The spots can also appear on the seeds (samaras).
The fungus winters-over on fallen leaves. If the leaves are not raked up in the fall, the fungal spores will reappear in the spring and spread to nearby trees. Treating the trees is usually not effective because the spores can travel from a neighbor's tree onto yours.
If your tree has these spots, which then causes leaves to curl in mid-July, it may have a different disease called Anthracnose.
Anthracnose is commonly mistaken for tar spot. However, it inflicts much more extensive damage because it affects both the leaves and the branches. You'll find many more spots on the leaves that are typically smaller than the 1/8" tar spots.
This condition typically occurs when trees experience long periods of cold, wet weather. The affected areas may show small, dark spots and irregularly-shaped leaves with dead or brown areas. The leaves usually fall off in the early spring, followed by a second set of leaves which also die off. The branches can also develop cankers, which often strip them of their bark and kill them.
The disease continues when fungal spores over-winter in dead leaves and infect trees during a prolonged wet spring. Once a tree is infected, the disease survive the winter in infected branches and then spread when the wind carries its spores to surrounding trees.
Anthracnose can be controlled by removing dead leaves from the base of your trees in the fall. You can also apply fungicide, but you may need a commercial application depending on the size and number of trees that may be affected. You can call your local Cooperative Extension office to see what fungicides are legal in your state.
Sooty mold feeds on the sticky honeydew left by aphids and scale insects, which can sometimes be found on maple trees. You'll know it's this mold if it rubs off easily on your fingers when you touch it.
The good news is that sooty mold won't kill your tree and can be easily treated. Try using a gardening mix that works to protect plants. Make sure to follow the instructions carefully and apply it at the base of the tree to ensure the roots absorb the mix ingredients. This method should also prevent reinfection for up to one year.
Lichen can be found on many maple varieties, but it's more commonly seen on mature trees. Fortunately, it's not harmful because it feeds off of the air rather than the trees.
You shouldn't feel a pressing need to eliminate lichen because it's not harmful, but you can use copper fungicides if you don't want to see them on your maples. Make sure to follow the instructions carefully!
One of the worst diseases that your tree can get is verticillium wilt. It affects the tree's vascular system, which usually kills the entire plant. The verticillium fungus is a soil-borne disease and can remain dormant in the soil years before it makes an appearance. The fungus enters through the tree's roots.
Two symptoms of verticillium wilt are yellowing leaves and wilting leaves. Sometimes, whole branches or the entire crown can wilt and die in a short period of time. You can also find a green or brownish green color in the sapwood of affected trees.
Try to get a proper diagnosis to help you make the right decision for your tree. Call your local Cooperative Extension office to see if they can come out and take a core sample to test.
Phytophthora root rot is caused by a wet spring or leaving your maple tree in poorly drained soil. The main symptoms are yellow, relatively-smaller sized leaves and dark brown or black tree roots.
Unfortunately, trees with root rot usually can't be salvaged and need to be cut down to prevent injuring people or damaging property.
Photos of Common Maple Tree IssuesClick thumbnail to view full-size
Additional Maple Tree Issues
You can see other issues that can affect your maple trees in the photos above. I'll try adding more as I come across additional issues, but feel free to examine these in case one helps you diagnose your tree's issues.