Every few springs, St. Louis gets the weather anthracnose loves: a cold, rainy April and May right as the sycamores and oaks are leafing out. A month later, homeowners in Webster Groves, Kirkwood, and Florissant are calling because the big sycamore in the front yard is dropping brown, curled leaves all over the driveway in June, or the white oak has papery blotches across its lower crown. It looks like the tree is dying. It almost never is. Thompson Tree Care and Landscaping has assessed hundreds of trees across the metro since 2014, and anthracnose is one of the most common, and least dangerous, problems we get called about. This guide explains what it is, which trees it hits, how to tell it from the diseases that actually kill trees, and the practical steps that keep it in check.
What is anthracnose?
"Anthracnose" is not a single disease but a family of them, caused by several closely related fungi that each favor a particular host. Apiognomonia species attack sycamore and oak; Discula destructiva is the one that goes after flowering dogwood; other species cover maple, ash, and walnut. What they share is a life cycle built around wet weather.
The fungus spends the winter in two places: on fallen leaves from last year and inside small cankers on infected twigs still on the tree. When buds break in spring, rain splashes spores from those sources onto the tender new leaves. Infection needs extended cool, wet conditions, roughly 50 to 60 degrees with the foliage staying damp, which is why a warm, dry April produces almost no anthracnose and a cold, soggy one produces a lot. Once summer heat arrives, the fungus goes quiet and the tree gets on with its year.
Because the disease is driven by weather rather than by anything wrong with the tree, a healthy sycamore can be badly defoliated one year and nearly clean the next without anyone doing a thing.
Which St. Louis trees get anthracnose, and what does it look like?
Symptoms vary by species, and knowing the pattern for your tree saves a lot of worry.
Sycamore and London Plane
Sycamore is the poster child for anthracnose in St. Louis. Look for irregular brown blotches that follow the veins of the leaf, young leaves that shrivel and turn black before they fully expand, and a heavy drop of leaves in May and June. The fungus also kills twigs, and repeated years of twig death produce clusters of crooked, stubby branches called "witches' brooms" that give old sycamores their gnarled look. The reassuring part: a defoliated sycamore pushes a second flush of leaves by July and looks nearly normal by August.
White Oaks
White oak, bur oak, and swamp white oak show papery, light-brown blotches along the leaf edges and veins, heaviest on the lower and inner branches where the canopy stays damp longest. Leaves may curl or drop early. Red oaks are affected far less often. If you are seeing browning on a pin or red oak in summer, read our guide to oak wilt in Missouri before assuming it is anthracnose.
Maples
Silver, sugar, and Norway maples develop irregular dead areas along the veins and leaf margins, sometimes with the leaf tearing where the dead tissue dries. Heavy infections cause early drop in wet springs, but the tree recovers.
Ash and Walnut
Ash anthracnose produces large brown blotches and scattered leaf drop; on black walnut, dark circular spots appear in early summer and leaves drop in August. Both are cosmetic. On ash, however, thinning from the top of the crown is a different and much more serious problem: see our guide to emerald ash borer in St. Louis.
Flowering Dogwood: The Exception
Dogwood anthracnose, caused by Discula destructiva, is the one member of this family that can kill its host. It begins as spreading purple-rimmed blotches on the leaves, moves into twigs, and then kills lower branches one at a time over several years, working upward. Trees in shade and in damp spots decline fastest. This one deserves early attention rather than a wait-and-see approach.
Is anthracnose the same as oak wilt or a dying tree?
No, and the difference matters because one is a nuisance and the other is a removal. The quickest way to sort them out is timing and direction.
- Anthracnose appears in spring, during or just after a wet spell. It concentrates on the lower and inner canopy, the blotches follow the leaf veins, and the tree releafs within weeks.
- Oak wilt appears in summer, often July. It starts at the top and outer edges of the crown, leaves brown from the margins inward and drop while still partly green, and a red oak does not recover. Read the full symptom comparison in our oak wilt guide.
- A dying tree shows problems that persist past the spring flush: bare branches that fail the scratch test, bark falling off, fungus at the base, or a crown that thins year after year. Our guide to the signs a tree is dead or dying walks through the checks you can do yourself.
A tree that dropped half its leaves in May and is fully green again by mid-July had anthracnose. A tree that is still bare in July has something else, and it is worth a look before the problem spreads.
How do you manage anthracnose?
Most of what controls anthracnose is sanitation and airflow, and most of it is work you can do or schedule in the off-season.
- Rake and dispose of fallen leaves in fall. Last year's leaves are next spring's spore source. Bag them or compost them well away from the tree rather than mulching them back under the canopy.
- Prune out dead twigs and cankers in winter. Dormant-season pruning removes the other overwintering site and lets the crew see the dead wood clearly. Thinning crowded interior growth also opens the crown so leaves dry faster after rain, which shortens the infection window. Our tree trimming and pruning crews schedule this work between November and February; see our guide to the best time of year to trim trees in Missouri for how it fits with other species.
- Water deeply in drought. A tree that lost leaves in May and then hits a dry July is working hard to rebuild. A slow soak every week or two during dry spells keeps it from stacking stresses.
- Keep sprinklers off the foliage. Overhead irrigation that wets the lower canopy in the evening recreates the damp conditions the fungus needs. Aim heads at the lawn, not the tree.
- Fertilize only on evidence. Anthracnose is not a nutrient problem. Fertilize when a soil test shows a deficiency, not as a reflex, since pushing soft new growth can make the next infection worse.
- Fungicide, selectively. Sprays work only when they go on at bud break, before symptoms appear, and are repeated through the wet season. On a 60-foot sycamore that costs real money for a cosmetic benefit, and the tree would have releafed anyway. Where it does pay off is on flowering dogwoods and on high-value specimen trees with a history of severe, repeated defoliation. Thompson Tree Care does not apply pesticides ourselves; we assess the tree and coordinate any treatment with a licensed applicator when it is warranted.
When is anthracnose a reason to remove a tree?
For sycamore, oak, maple, ash, and walnut, the honest answer is almost never. A mature shade tree can shrug off anthracnose for decades. Removal enters the conversation only when anthracnose is one stress among several: a tree that has been defoliated year after year, is also fighting drought or construction damage, and is now showing crown dieback that does not fill back in. At that point the question is no longer the fungus but the tree's overall decline, and a certified arborist assessment is the right next step.
Flowering dogwood is the exception. A dogwood that has been losing lower branches to anthracnose for several seasons, especially one growing in deep shade or a wet pocket, often reaches a point where it will not recover, and replacing it with a resistant cultivar or a native alternative is the practical choice.
If a tree does need to come out, our guide to tree removal cost in St. Louis explains the typical $300-$2,500 range and what drives it, and our tree removal crew handles everything from a small dogwood to a mature sycamore over a roof.
Thompson Tree Care and Landscaping is licensed and insured, has completed more than 500 jobs across St. Louis, Kirkwood, Chesterfield, Florissant, O'Fallon, and Belleville since 2014, and holds a 4.8-star Google rating from 60+ reviews. Estimates are free, and we offer senior and veteran discounts. If your tree is dropping blotchy leaves and you want to know whether it is anthracnose or something worse, call (314) 712-3035 or request an estimate online. For a broader look at what else might be going on, see our field guide to common tree diseases and pests in St. Louis.
Frequently Asked Questions
Almost never. Anthracnose on sycamore, oak, maple, ash, and walnut is a leaf and twig disease that flares in cool, wet springs and fades as the weather warms. The tree usually pushes a second set of leaves by early summer. Repeated years of heavy defoliation can weaken a tree, but the only anthracnose that routinely kills its host is dogwood anthracnose.
Usually not. Fungicides only work when applied at bud break, before symptoms appear, and they must be repeated through the wet season. For a large shade tree that pays off rarely. Sprays make sense mainly for high-value trees with a history of severe defoliation and for flowering dogwoods. Thompson Tree Care assesses the tree and coordinates any treatment with a licensed applicator.
Timing and direction. Anthracnose shows up in spring, hits the lower and inner canopy hardest, produces brown blotches that follow the leaf veins, and the tree releafs. Oak wilt appears in summer, starts at the top and outside of the crown, browns leaves from the edges inward, and a red oak does not recover. If you are unsure, get it assessed before pruning anything.
Prune during the dormant season, roughly November through February, when you can see the dead twigs and cankers clearly and the fungus is not spreading. Remove dead wood, thin crowded growth so leaves dry faster, and rake up and dispose of fallen leaves and twigs in fall. Never prune oaks between April and July because of oak wilt risk.
