3 Leaf Diseases That Can Affect Your Sugar Maple's Beauty

Sugar maple trees are known for producing maple syrup and for the vibrant, beautiful leaf color changes during autumn. Tree diseases that affect the leaves can strip your tree of its yearly show of beauty and leave your yard looking bare. While most leaf diseases don't pose any long-term dangers to the tree's health, cosmetic appeal is one of the main reasons to have a sugar maple and it's worthwhile to keep the leaves looking healthy.

Here are a few of the leaf diseases that can affect your sugar maple and how to stop the problem from spreading.


Anthracnose can be caused by several different kinds of fungi and thus can present with a range of symptoms that stretch beyond the leaves. Leaf symptoms include cankers or spots that form on the surface and wilting and early leaf shedding. The spreading disease can eventually cause twigs and branches to die off and cause the tree to look less full in the following growth year.

Anthracnose is fairly treatable by simply having a tree trimming company prune away the affected leaves and branches. Make sure leaves don't stay on the ground and don't use the affected leaves in compost for other plantings. Make sure the sugar maple tree isn't overwatered as wet conditions are a ripe breeding ground for the anthracnose fungi.

Powdery Mildew

Powdery mildew is so named for the fuzzy white coating that forms on leaves on the affected tree. The coating can block out the sunlight and thus stop photosynthesis, which forces the leaves into early shedding. The mildew is highly unattractive, especially on such an otherwise beautiful tree, but not actually damaging to the overall health of the sugar maple.

Pruning is often enough to keep powdery mildew managed and to prevent its return. You can also have your landscaper or tree service apply a fungicide as additional protection. Keep a closer eye for mildew occurrences during the spring or unseasonable summers where the nights are cool and the days warm and humid.  

Tar Spots

Tar spot causes yellowish dots to form on the leaves that emerge in the spring. As the season progresses, the dots will grow larger and larger and eventually turn black like tar. Once the leaves turn black, photosynthesis is usually sufficiently interrupted that the leaves will then shed off the tree.

Tar spots are mostly a cosmetic issue and won't necessarily come back next year even if you take no action. If you want to be safer, you can ask a tree service (like Carlos Tree Service Inc) to trim away affected leaves and to apply a protective fungicide that minimizes the chance of the disease returning.