✓ Low Urgency

Black Spots on Tree Leaves

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What It Means Causes Trees Affected How Urgent What To Do Call an Arborist?Regional Notes Related Pests FAQ

What This Symptom Usually Means

Black spots on tree leaves are almost always caused by fungal diseases. The good news: most leaf spot diseases are cosmetic and do not significantly harm the tree. The pattern, size, and timing of the spots help identify the specific fungus. Tar spot on maples is the most common — raised, shiny black spots that look like drops of tar. Apple scab causes olive-to-black spots on crabapple and apple leaves. Sooty mold (which grows on honeydew from insects) creates a black coating that wipes off.

Most Likely Causes

Tar spot (Rhytisma)

Raised, shiny black spots up to 1/2 inch across on maple leaves. Purely cosmetic — does not harm the tree. Extremely common in the Midwest and Northeast.

Apple scab

Olive-green to black spots on crabapple and apple leaves. Causes significant leaf drop in wet years. Some cultivars are resistant.

Leaf spot diseases (various fungi)

Small black or brown spots caused by Septoria, Phyllosticta, and other fungi. Mostly cosmetic. Favor wet conditions.

Sooty mold

Black coating that covers the entire leaf surface. Grows on honeydew (sticky excrement) produced by aphids, scale, or whiteflies. The real problem is the insect infestation.

Black knot

Hard black growths on branches (not leaves) of cherry and plum trees. The fungus Apiosporina morbosa causes progressively larger galls that can kill branches.

Bacterial leaf spot

Angular black spots between leaf veins. Spots may have a yellow halo. More common in warm, humid conditions.

Trees Commonly Affected

Maple

Tar spot is nearly universal on Norway, silver, and red maples

Crabapple

Apple scab is the most common disease — choose resistant cultivars

Cherry/Plum

Black knot is a serious branch disease, not just leaf spots

Sycamore

Anthracnose causes dark blotches on leaves in wet springs

Dogwood

Spot anthracnose causes small purple-bordered spots

Linden

Sooty mold on leaves from aphid honeydew dripping from above

How Urgent Is This?

✓ Low Urgency

Low for most leaf spot diseases. Tar spot and most leaf spots are cosmetic and do not require treatment. Apple scab is moderate urgency if it causes heavy defoliation year after year — consider replacing susceptible trees with resistant cultivars. Black knot on cherry and plum is high urgency because it spreads and can kill branches. Sooty mold indicates an insect problem that may need attention.

What You Can Do Right Now

Identify the spot type: raised and shiny (tar spot), olive-to-black irregular (apple scab), wipes off (sooty mold), on branches not leaves (black knot).
Rake and dispose of fallen leaves in fall to reduce fungal spore load next spring — this is the single most effective management step.
For sooty mold, identify and treat the insect infestation (aphids, scale) that is producing honeydew.
For apple scab on crabapples, consider replacing with a resistant cultivar when the tree declines.
For black knot, prune infected branches 6-8 inches below the visible gall during winter dormancy.
Avoid overhead watering — wet foliage promotes fungal infection.

When to Call a Certified Arborist

Contact a certified arborist if any of these apply:

✓Black knot galls are spreading to major branches or the trunk
✓Apple scab causes heavy defoliation for multiple consecutive years
✓You cannot identify the cause and want a professional diagnosis
✓Sooty mold is heavy and you need help identifying the insect source
✓A commercial orchard or high-value specimen is affected

Find an Arborist Near You

State & Regional Differences

Midwest

Tar spot on maples is extremely common and often causes alarm, but is harmless. Apple scab is severe on susceptible crabapples in wet years.

Southeast

Warm, humid conditions promote bacterial leaf spots. Cercospora leaf spot is common on many ornamental species.

West

Leaf spots are less common in dry climates. When they occur, they are usually associated with overhead irrigation.

Northeast

Tar spot and apple scab are both very common. Black knot on cherry trees is a significant problem throughout the region.

Frequently Asked Questions

Are black spots on maple leaves harmful?

In most cases, no. Tar spot (Rhytisma) causes raised, shiny black spots on maple leaves. It is purely cosmetic and does not harm the tree's health, growth, or structural integrity. No treatment is necessary. Raking fallen leaves in autumn reduces the number of spores available to infect new leaves the following spring.

Should I spray fungicide for leaf spots?

For most leaf spot diseases on landscape trees, fungicide sprays are not recommended. The diseases are cosmetic, and spraying a large tree is expensive, difficult, and has environmental impacts. The exception is apple scab on high-value fruit or crabapple trees, where preventive fungicide sprays starting at bud break can reduce infection. For landscape trees, cultural practices (leaf cleanup, proper spacing, avoiding overhead watering) are more appropriate.