If your maple has black spots on its leaves in late summer, the first thing to know is that the tree is very rarely in danger. Most black spotting on maples is tar spot, a leaf disease that looks far worse than it is. This guide shows you how to recognize it, how to rule out the few look-alikes, and what is worth doing about it.

Table of Contents

The short answer: raised, glossy black spots that look like drops of tar are tar spot, a fungal leaf disease. It is mostly cosmetic. Rake up and dispose of the fallen leaves in autumn, keep the tree watered in dry spells, and skip the fungicide. Flat brown or purple blotches along the veins in spring point to anthracnose instead, which is also usually minor.

What tar spot looks like

Tar spot is caused by fungi in the genus Rhytisma. The disease starts in early summer as small, pale yellow-green spots on the upper side of the leaf. By midsummer a black, raised patch forms in the middle of each spot, and by late summer the patches look shiny, thick and slightly wrinkled, as if someone flicked tar onto the leaves.

The size of the spots tells you which species you are dealing with. On Norway maple and sycamore maple the patches are large, often half an inch to more than an inch across. On red and silver maple you tend to see many small black specks clustered together instead. Both are tar spot.

What you see	Likely cause	How serious
Raised, shiny black patches, late summer	Tar spot	Cosmetic
Clusters of tiny black specks, red or silver maple	Tar spot (speckled type)	Cosmetic
Brown or purple blotches along the veins, spring	Anthracnose	Usually minor
Brown, crispy leaf edges in hot weather	Leaf scorch	Watering problem
Black sooty film that wipes off	Sooty mold from aphid honeydew	Minor, check for aphids

Is tar spot harmful?

Extension specialists at the University of Wisconsin and UConn both describe tar spot as mainly an aesthetic problem. The fungus infects the leaves, not the branches, trunk or roots. In a heavy year the leaves can drop a few weeks early, which looks alarming, but a healthy, established maple has already done most of its growing for the season by then.

Where it does matter is when tar spot stacks on top of other stress. A young tree that was just planted, a maple squeezed into a small strip next to a driveway, or a tree that went through a long drought is less able to shrug off early leaf loss. In those cases the fix is still not a spray. It is better care: deep watering during dry spells and a ring of mulch.

Why it keeps coming back

The fungus spends the winter on the fallen leaves. In spring, as new leaves open, it releases spores from those old leaves and the wind carries them up into the canopy. Cool, wet springs mean more infection, which is why tar spot can be bad one year and barely visible the next.

This life cycle is also why one cleanup step is so effective. Penn State Extension and UConn both recommend raking up and removing fallen maple leaves in autumn. Bag them, put them out with yard waste that leaves your property, or compost them in a hot, active pile. Leaves left to sit in a flower bed under the tree are next year’s infection.

What to do about tar spot

Confirm it. Look for raised, shiny, black patches with a pale yellow edge, on the upper leaf surface only.
Rake and remove fallen leaves in autumn, including those under shrubs and along fences.
Water deeply during dry spells, especially for trees planted in the last three years.
Leave the fungicides on the shelf. Extension guidance is that sprays are rarely justified for tar spot in a home landscape. They have to go on at bud break, they need repeat applications, and full coverage on a large maple is not practical.
If your neighbors have the same maples, the spores will blow in from their trees too. Cleanup still reduces the load, but do not expect zero spots.

Look-alikes worth ruling out

Anthracnose shows up earlier, in cool, wet spring weather. The spots are brown, tan or purplish and follow the veins rather than sitting as raised black patches. Michigan State University notes that maples usually recover and push new leaves once the weather warms. It is another reason to rake.

Sooty mold is a black, powdery coating that rubs off with a finger. It grows on the sticky honeydew from aphids or scale insects feeding higher in the tree. The problem to look at there is the insects, not the mold.

Leaf scorch turns the edges and the tissue between the veins brown and crisp during hot, dry or windy weather. It is a water problem, not a disease, and it often appears on the side of the tree that gets the most sun or reflected heat from pavement.

If the spots are on the bark or the branches rather than the leaves, or if the tree is wilting on one side, that is a different situation. Start with my symptom-by-symptom maple guide instead.

When to call a certified arborist

Tar spot alone almost never needs professional help. Call a certified arborist if the leaves are spotted and the tree also has dead branches, wilting, thinning in the crown year after year, or cracked bark at the base. Those signs point to a deeper problem, and the spots are just the part you noticed first. You can find certified arborists through the ISA Find an Arborist directory, and your county extension office can usually identify a leaf sample for you.

For more on maple troubles, see why a maple may be slow to leaf out and the rest of the Tree Problems & Diagnosis hub.

Sources

Tar Spot, University of Wisconsin–Madison Extension
Tar Spot of Maple, UConn Home and Garden Education Center
Maple Diseases, Penn State Extension
Anthracnose: Diseases of Shade Trees, Michigan State University Extension

Top photo: Saforrest, CC BY-SA 3.0, via Wikimedia Commons

Black Spots on Maple Leaves: Tar Spot and Its Look-Alikes