What causes black spots on tree leaves?
Dark spots, blotches, or raised tarry patches scattered across the leaves — sometimes discrete circles, sometimes irregular areas that follow the veins.
Watch it, correct the care behind it, and check again next season. Nothing here threatens people or property in its current state.
Nearly every leaf-spot disease in Kansas is a cosmetic problem on an established tree. Leaves are a one-season crop, and a tree that loses part of that crop in June still has July through September to work. Repeated total defoliation year after year, or leaf spots on an evergreen, are the exceptions worth taking seriously.
What this looks like
The shape of the marking is the diagnosis. Small, evenly round spots with a defined border are one family. Large irregular blotches that spread along the midrib and main veins are another. Raised, glossy black patches that look painted on are a third. And an even, sooty film that covers the whole upper surface and wipes off with a damp cloth is not a leaf disease at all.
- Round, sharply bordered spots, sometimes with a lighter center or a yellow ring
- Irregular brown-black blotches spreading outward from the veins, with early leaf drop
- Raised, shiny black patches up to half an inch across on maple leaves
- A uniform dark film that rubs off between your fingers and leaves the leaf green underneath
What causes it in Kansas
Roughly in order of how often each turns out to be the answer here. The line under each one is what separates it from the others — open a cause for the detail.
1Anthracnose
How to tell: Brown to black blotches that follow the veins, curled and shriveled young leaves, and a carpet of dropped foliage under the tree in late May.The most consequential leaf disease in a wet Kansas spring, especially on sycamore, where it also kills expanding shoots and forces the tree to leaf out twice. Ash, maple, oak, and walnut have their own strains. Severity tracks April and May rainfall almost exactly.
2Tar spot
How to tell: The spot is raised enough to feel with a fingertip and looks like a drop of asphalt on the blade.A fungus of maples that produces thick, raised, tar-black spots with a yellow halo. It is dramatic and nearly harmless — the affected leaf keeps functioning around the spot, and the tree is not weakened.
3Common leaf spot fungi
How to tell: Small round spots of consistent size, most numerous on the lower interior branches where leaves stay wet longest.Dozens of species produce small circular lesions on hackberry, redbud, sycamore, mulberry, and elm after a wet spring. They overwinter in fallen leaves and reinfect from below.
4Cedar rusts
How to tell: Rust-orange spots with tiny raised tubes on the leaf underside, on a crabapple or hawthorn growing within a few hundred yards of cedars.Kansas has eastern red cedar in every fence line, and it hosts rust fungi that spend the other half of their life on crabapple, hawthorn, and serviceberry. The result on the broadleaf host is bright orange-yellow spots, not black ones — and orange gelatinous galls on the cedar in spring.
5Sooty mold on honeydew
How to tell: It wipes off. Nothing is damaged underneath, and the leaves are sticky before they are black.Aphids and soft scale excrete sugar; a harmless black fungus grows on the sugar. The tree is not infected. Everything under the canopy — leaves, cars, patio furniture — gets the same coating.
6Hail and physical injury
How to tell: Damage concentrated on the storm-facing side, torn rather than round margins, and matching bruises on nearby annuals and vegetable leaves.Kansas hail punches holes and bruises leaf tissue that darkens as it dies, and the pattern is easy to mistake for disease a week or two after the storm.
What to do, and what to avoid
Safe to check yourself
All from the ground — no ladder, no saw.
- Try to rub a spot off with a wet cloth before assuming it is a disease
- Look at whether the spots follow the veins or ignore them — that single observation separates anthracnose from everything else
- Check the leaf underside for raised tubes, fuzz, or insects
- Count how much of the canopy is affected; under a third is a cosmetic year
What not to do
The responses that make this one worse or permanent.
- Do not spray a fungicide once spots have appeared — foliar fungicides are preventive, applied at bud break, and useless afterward
- Do not leave heavily infected sycamore or crabapple litter under the tree, since spores overwinter there and start next spring's cycle
- Do not fertilize to push a second flush of growth; new tissue during a wet spring is exactly what the fungus wants
- Do not prune a tree in wet weather to clean it up, which moves spores around on your tools
When to contact an arborist
Whatever this narrows it down to, the assessment that decides what happens next has to happen at the tree. Why that is
Common questions
Should I rake and destroy the leaves?
Should I rake and destroy the leaves?
For sycamore anthracnose, crabapple scab, and rust, yes — those fungi overwinter in fallen leaves and infected twigs, and removing the litter measurably reduces next year's pressure. For tar spot on a big maple, the spores travel far enough that raking your own yard accomplishes very little.
My sycamore lost every leaf in May and grew new ones in June. Is it dying?
My sycamore lost every leaf in May and grew new ones in June. Is it dying?
No. That is the standard sycamore response to a cool, wet Kansas spring and it happens repeatedly over a long life. Watch for shoot dieback and progressively sparser crowns over several years, which would be the point at which the pattern starts to cost the tree something real.
Can I do anything preventive for next year?
Can I do anything preventive for next year?
Improve air movement and reduce leaf wetness: thin crowded interior branches during dormancy, avoid running sprinklers into the canopy, and clean up litter. Preventive fungicide programs exist for high-value specimens, but they must start at bud break and be repeated, which is why they rarely make sense for a large shade tree.
Kansas Tree Guide is an independent educational resource. Nothing on this site replaces an on-site assessment by a qualified arborist or tree-care professional. Last reviewed August 2026.
Often seen alongside this
A second symptom narrows the cause faster than more detail about the first.
Not what you are seeing? Work the symptom guide again.