Anthracnose on Trees: What It Looks Like and When to Actually Worry

Your sycamore looked dead in April. Half the new leaves turned brown and curled before they even finished unfolding, and a few dropped straight to the ground. By July the same tree has a full, green canopy and you’d never know anything happened. That’s anthracnose, and it’s the most common tree disease call I get every spring.

Anthracnose is a group of related fungi that attack new leaves and shoots during cool, wet weather. It hits sycamore and London plane hardest, and it’s common on oak, ash, maple, and dogwood too. For our full rundown on when a tree’s decline points to something worse, see our signs of a dying tree guide. For the wider fungal picture, our tree fungus guide covers root rot and other fungi that are actually dangerous.

Here’s what anthracnose looks like, which trees get hit worst, and the one species where this “harmless” disease turns serious.

How to tell it’s anthracnose

The tell is the pattern, not just the color. Anthracnose produces irregular brown, tan, or black blotches that run along or between the leaf veins, not neat round spots with a clean edge. The blotches often start right at the vein and spread outward, so a damaged leaf looks streaked rather than uniformly speckled.

A few more identifiers:

• Timing. Symptoms show up in April and May in most of the country, right as new leaves emerge. By July the tree looks fine again. If you’re seeing this exact pattern repeat every wet spring and clear up every summer, that’s anthracnose, not a chronic disease.
• Distorted new growth. Infected leaves often curl, cup, or twist as they expand, because the fungus killed part of the leaf tissue before it finished growing.
• Twig dieback on the worst-hit trees. On sycamore especially, the fungus kills buds and young twig tips before leaves even emerge, which can look like the tree failed to leaf out at all in one section of the canopy.
• Premature leaf drop, especially low and inside the canopy. The lower, shadier branches usually show the heaviest damage because that’s where moisture lingers longest after rain.
• Weather match. Anthracnose needs cool temperatures right at bud break. Mean daily temperatures between 50°F and 57°F during leaf emergence are the sweet spot for infection, according to the Morton Arboretum. Once daily temperatures push consistently above 60°F, new infections mostly stop. A cold, rainy April followed by a hot May is the exact recipe for a bad anthracnose year followed by a fast recovery.

If what you’re looking at is round, angular purple-bordered spots that show up in August rather than April, you’re more likely dealing with a leaf spot fungus like septoria, not anthracnose. And if an entire branch wilts and browns fast in June while the rest of the tree looks normal, stop reading about anthracnose and go check for oak wilt or Dutch elm disease instead. Those move through the vascular system and can kill a tree in weeks.

Which trees get hit, and how bad

Anthracnose isn’t one fungus. It’s a handful of related species, each specific to a tree genus, that all show up under the same weather conditions and produce similar symptoms. That’s why your sycamore, oak, and maple can all look rough in the same wet April without one infecting the other.

Sycamore and London plane: the worst of the bunch

Sycamore (Platanus occidentalis) and its close relative London plane (Platanus x acerifolia) take the hardest hit of any species. Sycamore anthracnose (Apiognomonia veneta, asexual stage Discula platani) is described by Clemson HGIC as the most serious fungal disease affecting American sycamore in the Southeast, and the pattern is consistent nationwide.

On sycamore, the fungus attacks buds and young twigs before leaves even open, so a bad spring can look like the tree failed to leaf out on entire branches. Once leaves do emerge, they show heavy blotching, curling, and early drop. Repeated years of severe infection also trigger “witches’ broom,” a cluster of small shoots that grows from a bud the fungus damaged instead of killed outright.

Even with the dramatic spring appearance, established sycamores recover. If you’re planting new and want to skip this problem, London plane cultivars ‘Bloodgood,’ ‘Columbia,’ and ‘Liberty’ carry meaningfully better resistance than seed-grown trees, per Clemson HGIC.

White oak: more susceptible than you’d guess

Oak anthracnose hits the white oak group (white oak, bur oak, swamp white oak) noticeably harder than the red oak group (red oak, pin oak, black oak), according to University of Minnesota Extension. If you’ve got a white oak that looks scorched every wet spring while a nearby red oak stays clean, that split in susceptibility is why.

Ash: green ash takes it worse than blue ash

Ash shows the same pattern of uneven susceptibility. Green ash and Chinese ash pick up anthracnose more readily, while blue ash shows meaningfully better resistance. Symptoms follow the standard playbook: vein-associated blotching, curling, and a spring flush that looks worse than the tree actually is.

Maple: a spring scare that fades by summer

Maple anthracnose (Aureobasidium apocryptum) shows up as brown, irregular dead patches along and between the veins, and it can look alarming. A bad year can cost a sugar maple or red maple 30 to 50 percent of its early leaves. Our maple tree diseases guide covers this species-by-species alongside the one maple disease that’s genuinely dangerous, verticillium wilt. The short version: anthracnose is the spring problem your maple grows out of. Verticillium is the summer problem that gets worse every year. Don’t confuse the two.

Oak, again, in more detail

If you want the full oak disease picture, including how anthracnose compares to Sudden Oak Death and Armillaria root rot, our oak tree diseases guide covers all of it. The short version for anthracnose specifically: cosmetic on mature oaks, occasionally worth watching on a young or high-value tree.

Elm: yes, elm gets it too

Elm anthracnose is a separate, less publicized problem from Dutch elm disease, and it’s far less dangerous. Our elm tree diseases guide covers where it fits alongside the diseases that actually threaten elms.

The dogwood exception

Every species above follows the same reassuring pattern: ugly in spring, fine by summer, don’t spend money on it. Flowering dogwood breaks that pattern completely.

Dogwood anthracnose (Discula destructiva) is a different, far more aggressive fungus than the anthracnose species hitting sycamore, oak, ash, and maple. It was introduced from Asia in the late 1970s, and Cornus florida had no natural defense against it. The disease swept through wild dogwood populations in the Appalachian and Northeastern forests through the 1980s and 90s, killing millions of trees, and it’s still killing backyard dogwoods today.

Unlike the cosmetic version on shade trees, dogwood anthracnose moves from the leaves into the twigs, then into the trunk, producing cankers that progress over multiple years and eventually girdle and kill the tree. There is no cure once it reaches the trunk. Our dogwood tree diseases guide covers the full identification, treatment, and resistant-cultivar picture in detail, including which Cornus kousa hybrids sidestep the problem entirely.

The practical takeaway: if you’ve got a sycamore or an oak with anthracnose, don’t panic and don’t spend money you don’t need to. If you’ve got a flowering dogwood with brown, purple-margined spots and any sign of a twig or trunk canker, treat it like the real threat it is and act early.

The disease cycle, in plain terms

All of these fungi run on the same basic clock, which is why the timing advice below works across species.

1. Overwintering. The fungus spends the cold months in infected twigs, buds, and cankers on the tree, and in fallen leaves on the ground underneath it.
2. Spring spore release. As buds break, rain and wind carry spores from that overwintered material onto the newly emerging leaves and shoots.
3. Infection window. If the days around bud break stay cool and wet (roughly 50-57°F with rain), the spores infect the tender new tissue. If the weather turns warm and dry instead, most of those spores never get a foothold.
4. Secondary spread. Infected leaf and twig tissue produces a fresh round of spores that can spread further through the canopy during the same wet stretch, which is why a single soggy week in April can do more damage than a whole rainy month spread thin.
5. Recovery. Once the weather dries out and warms past about 60°F, new infections stop. The tree drops the damaged leaves and pushes a second flush, usually complete by June or July on most species.

That cycle is also why the same tree can have a brutal anthracnose year one spring and barely show symptoms the next. It’s not about the tree getting sicker or healthier. It’s almost entirely about how cold and wet April happened to be.

Treatment: sanitation first, spray only when it’s earned

For sycamore, oak, ash, and maple, treat anthracnose as a cosmetic problem you manage, not a disease you cure.

Rake and remove infected leaves in fall. This is the single highest-value thing you can do. The fungus overwinters in fallen leaf litter, so clearing it out reduces next spring’s spore load. Bag it or haul it off. Don’t leave it in a pile against the trunk, and don’t compost it near other susceptible trees.

Prune for airflow and remove dead twigs. Open up dense, shaded interior growth during the dormant season (winter, before bud break). Better air circulation means faster leaf drying after rain, which slows fungal spread. While you’re in there, cut out twigs and small branches that died back from a bad infection the year before. A pair of Felco F2 bypass pruners makes clean cuts that heal fast, and sanitizing the blade with rubbing alcohol between cuts on a heavily infected tree keeps you from spreading spores on the tool itself.

Water during drought stress. A tree already stressed by dry summers recovers from anthracnose damage more slowly. Deep, infrequent watering at the dripline through hot, dry stretches helps the tree push that second leaf flush without added strain.

Fungicide, only for the trees that justify it. By the time you can see anthracnose damage, spraying does almost nothing. Fungicide only works as a preventive, applied at bud break and again 10-14 days later, before symptoms appear. That timing only makes sense on a small number of trees: a young dogwood in a high-anthracnose region, an ornamental you paid real money for, or a shade tree that’s had three consecutive severe years in a row. Bonide Copper Fungicide applied at full label rate at bud break, then again about two weeks later, is the standard home approach. On a mature 40-foot sycamore or oak, skip the spray. There’s no practical way to cover the whole canopy, and the tree will recover without it.

Dogwood anthracnose is the one place where I’d push harder on fungicide. If you’ve got a Cornus florida with early leaf symptoms and no trunk cankers yet, the same copper fungicide schedule, applied consistently every spring, can genuinely slow the disease’s progress toward the trunk. Full details on dosing and timing for dogwood specifically are in our dogwood tree diseases guide.

Prevention checklist

Six habits handle almost every anthracnose case you’ll run into:

• Rake and dispose of fallen leaves every autumn. Cuts next spring’s spore source more than any other single step.
• Prune in the dormant season, not in a wet spring. Remove dead twigs and open up crowded interior growth before bud break.
• Improve drainage and air circulation around the tree. Standing water and dense, shaded plantings keep leaves wet longer after rain, which favors infection.
• Don’t let sprinklers wet the canopy. Overhead irrigation mimics the same wet-leaf conditions that spring rain creates. Switch to drip or soaker hoses at the root zone.
• Avoid heavy nitrogen fertilizer in spring. It pushes soft new growth that anthracnose infects more readily.
• Choose resistant cultivars when planting new. London plane ‘Bloodgood,’ ‘Columbia,’ or ‘Liberty’ for sycamore-type trees, and resistant dogwood cultivars if you’re planting a flowering dogwood in a region where anthracnose pressure runs high. Our dogwood tree diseases guide lists the specific resistant series worth seeking out at the nursery.

When to call an arborist

Most anthracnose cases on shade trees don’t need a professional at all. Rake the leaves, prune in winter, water through drought, and let the tree do the rest. Call in help when you see any of these:

• A flowering dogwood with cankers on the trunk, not just spotted leaves. Once dogwood anthracnose reaches the trunk, the treatment window narrows fast, and an arborist can assess whether the tree is worth aggressive treatment or better replaced.
• Three or more consecutive severe years on the same tree. A tree that can’t shake anthracnose for that long may be dealing with an underlying stress problem (poor drainage, root damage, a bad planting site) that needs diagnosis beyond the fungus itself.
• You can’t tell anthracnose from something worse. Rapid whole-branch wilting, especially on oak or elm in early summer, needs a same-week look to rule out oak wilt or Dutch elm disease, both of which move far faster than anthracnose and require prompt action.
• A high-value or specimen tree. If you’re not confident applying fungicide timing correctly on an ornamental you paid a lot for, a licensed applicator can handle the spray schedule for you.

An arborist consultation runs $75-200 in most markets. Find an ISA-certified arborist through Trees Are Good, or read our guide to what an arborist does before you hire anyone. If you’re not sure whether what you’re seeing points to a bigger problem than anthracnose, our signs of a dying tree guide walks through the four broader causes of tree decline and which one fits your situation. And if the underlying issue turns out to be drought stress rather than disease, our watering guide for newly planted trees covers the schedule that prevents a lot of these problems before they start. Mklibrary.com’s guide to the camphor tree covers anthracnose alongside armillaria, phytophthora, and verticillium wilt on that species, if you’re weighing camphor as a shade tree and want the fuller disease picture before you plant.

Frequently Asked Questions

Is anthracnose going to kill my tree?

Almost never, with one exception. On established shade trees like sycamore, oak, ash, and maple, anthracnose is a cosmetic wet-spring problem. The tree drops some early leaves and pushes a second flush by midsummer. The exception is dogwood anthracnose (Discula destructiva), which can girdle the trunk and kill a flowering dogwood over several years if it goes unmanaged.

Why does my tree look terrible in May but fine by July?

That’s the anthracnose pattern. Cool, wet weather at bud break (roughly 50-57°F) lets the fungus infect new leaves and shoots. Once temperatures climb past 60°F and stay dry, the fungus stops spreading. The tree drops the damaged leaves and grows a clean second flush, usually by June or July.

Should I spray my tree for anthracnose every year?

Usually no. Fungicide only makes sense on small, high-value trees (a young dogwood, an ornamental you paid real money for) or after three consecutive bad years on the same tree. On a mature shade tree, sanitation (raking leaves, pruning dead twigs) does almost as much good as spraying, for a fraction of the cost.

What’s the difference between anthracnose and oak wilt or Dutch elm disease?

Anthracnose follows leaf veins, shows up in spring, and the tree recovers by summer. Oak wilt and Dutch elm disease are vascular diseases that cause rapid, often fatal wilting through the whole crown, sometimes within weeks. If a branch is wilting fast in June or July rather than looking spotty in April, you’re probably not looking at anthracnose.

Can anthracnose spread from my sycamore to my oak next to it?

Not directly. Each tree genus has its own anthracnose fungus. The species on sycamore (Apiognomonia veneta) doesn’t infect oak, and the oak species doesn’t infect maple. What can happen is that the same cool, wet spring triggers anthracnose on several different tree species in your yard at once, which looks like it’s spreading but is really several separate infections responding to the same weather.

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References: Morton Arboretum, Anthracnose of Shade Trees; Penn State Extension, Anthracnose on Shade Trees; Clemson HGIC, Sycamore Diseases and Insect Pests; University of Minnesota Extension, Anthracnose in Trees and Shrubs.