Anthracnose on sycamore
Every wet spring, sycamore trees in the eastern US appear to be dying. Leaves brown and fall. Entire branch tips die back. Alarmed homeowners call arborists and Extension offices in large numbers. In almost every case, the diagnosis is the same: sycamore anthracnose, a cool-weather fungal disease.
—- title: "Anthracnose on sycamore" slug: anthracnose-on-sycamore hub: problems category: "Disease-by-host" description: "Sycamore anthracnose defoliates trees every wet spring. Understand the cool-weather disease cycle, why healthy sycamores almost always recover, and when fungicide is actually warranted." date: 2026-06-10 updated: 2026-06-10 author: "Thomas A." reading_time: 8 —-
Every wet spring, sycamore trees in the eastern US appear to be dying. Leaves brown and fall. Entire branch tips die back. Alarmed homeowners call arborists and Extension offices in large numbers. In almost every case, the diagnosis is the same: sycamore anthracnose, a cool-weather fungal disease that is severe in appearance but rarely fatal to the tree.
Sycamores are among the most anthracnose-susceptible trees in the eastern US. The disease is so common and predictable that a sycamore without anthracnose symptoms in a wet spring is the exception. The practical good news: most established sycamores releaf by mid-June and continue growing with no lasting structural damage.
I don't grow sycamores at my Long Island property, so this guide is sourced from University Extension and USDA Forest Service research.
The pathogen
Sycamore anthracnose is caused by Apiognomonia veneta (formerly classified as Gnomonia leptostyla var. platani). Per University of Minnesota Extension, this fungus overwinters in infected twig tissue and on fallen leaves. Spores are released during cool, wet weather in spring, infecting expanding leaves, shoots, and small twigs. Infection slows dramatically as temperatures rise above 60°F (16°C) in late spring.
The same fungal genus infects other tree species, but each form is host-specific. Apiognomonia veneta infects only Platanus species (sycamore, London planetree).
Identification
Symptoms by timing
Per Clemson HGIC, sycamore anthracnose progresses through predictable phases:
Phase 1 — Bud blight (April): Expanding buds and very young shoots turn brown and die before leaves fully open. In severe infections, entire shoot ends die back. From a distance, the tree looks like branches failed to leaf out.
Phase 2 — Shoot blight (early May): Young shoots and leaves infected after opening wilt, brown, and hang on the tree. This creates the hanging-dead-leaf appearance that alarming homeowners.
Phase 3 — Leaf spots (late May): On leaves that emerged and expanded before infection, large irregular brown patches develop along leaf veins. The vein-associated pattern is characteristic: the browning follows major veins with irregular tan-brown tissue dying outward from the vein.
Phase 4 — Twig dieback: Small terminal twigs (less than 0.5 inch diameter) killed by cankering die and remain on the tree as dead, brown stubs. In successive years, these dead stubs give the lower and mid-canopy a sparse, ragged appearance.
The "shepherd's crook"
Per Penn State Extension, infected shoot tips curl and die in a characteristic hook shape — called "shepherd's crook" — as the rapidly growing tip dies while the base of the shoot is still alive. This symptom is also seen in fire blight on pears and in botrytis dieback, but on sycamore in spring the cause is almost certainly anthracnose.
What it is not
Per University of Minnesota Extension, bark scaling, lichens, and normal sycamore exfoliation are frequently misidentified as disease. The peeling, mottled bark of sycamore is normal. Anthracnose affects living foliage and small-diameter twig tissue, not bark.
Why sycamores survive
Per Clemson HGIC, sycamores have an important adaptation: the buds in the axils of infected, lost leaves (latent buds along the twig) reactivate and produce a second flush of foliage once temperatures warm and fungal activity slows. By June or July, most sycamores have largely releveled. This second flush is typically disease-free because warm summer conditions inhibit the pathogen.
Repeated defoliation over multiple consecutive wet springs can weaken a tree over time. Per Penn State Extension, mortality is rare but has been documented in trees that experienced severe anthracnose for 5 or more consecutive years while also facing other stresses (drought, root compaction, secondary infections).
Species and cultivar susceptibility
Per NC State Extension, susceptibility varies significantly:
- Platanus occidentalis (American sycamore) — very susceptible; the species most commonly affected
- Platanus orientalis (Oriental plane tree) — substantially more resistant; less common in cultivation
- London planetree (P. × acerifolia) — intermediate susceptibility; widely planted as a street tree; cultivar 'Bloodgood' is more resistant than the species
- 'Columbia' and 'Liberty' cultivars — selected for resistance; perform better in high-pressure years
Per Cornell Cooperative Extension, for sites where anthracnose is a consistent annual problem, choosing London planetree 'Bloodgood' or 'Columbia' over American sycamore reduces disease impact significantly.
Management
Maintain tree health
Per University of Minnesota Extension, the primary management strategy is keeping the tree vigorous:
- Water during drought (1 inch per week equivalent during dry summers)
- Maintain 3–4 inches of organic mulch over the root zone to the drip line
- Avoid soil compaction over roots
- Limit pruning to the dormant season
Rake and dispose of fallen leaves
Per Penn State Extension, fallen infected leaves and dead twigs are primary inoculum sources. Rake and dispose of debris in autumn and early spring before bud break. Do not compost infected material — dispose in the trash.
Pruning
Per Clemson HGIC, prune out dead twigs and small branches in late winter before bud swell. This removes overwintering fungal tissue from the canopy. On large trees, professional pruning is necessary to address upper canopy material.
Fungicides
Per Penn State Extension, preventive fungicide applications can reduce severity in high-value young trees (small enough to spray thoroughly) or in consecutive high-pressure years when trees show significant decline. Apply at bud break and repeat every 10–14 days until leaves are fully expanded. Registered active ingredients include copper fungicides, thiophanate-methyl, and propiconazole.
On large, established sycamores, fungicide application is impractical from the ground and expensive when hired out. Per University of Minnesota Extension, preventive spraying of large trees for anthracnose is generally not cost-effective unless the tree is in serious decline after multiple consecutive severe infections.
Common problems table
| Symptom | Likely cause | Action |
|---|---|---|
| Brown, dead shoot tips in early May | Anthracnose shoot blight | Normal spring disease; tree will releaf |
| Leaves browning along veins in May | Anthracnose leaf blight | Wait for warm weather; tree will flush again |
| Dead twigs throughout canopy by June | Anthracnose twig dieback | Prune dead twigs in fall or late winter |
| Tree does not releaf by late June | Severe stress or other disease | Arborist consultation warranted |
| Peeling mottled bark on trunk | Normal sycamore exfoliation | Not disease; no action needed |
Frequently Asked Questions
Should I spray my sycamore every spring?
Per University of Minnesota Extension, no — not for established, large trees. The disease is cosmetically unpleasant but rarely threatens the tree's life. Spraying large trees is expensive, difficult to do thoroughly, and rarely cost-effective. Reserve fungicide programs for young trees in decline or high-value specimens in consecutive severe years.
My sycamore looks terrible in May. Will it recover?
Per Clemson HGIC, almost certainly yes. The second leaf flush from latent buds typically restores most of the canopy by early summer. A sycamore that looks severely blighted in May often looks reasonably normal by July.
Does the disease spread to other trees in my yard?
Per Penn State Extension, Apiognomonia veneta is host-specific to Platanus. It does not spread to maples, oaks, dogwoods, or other landscape trees.
Are there sycamore cultivars worth planting instead of the standard species?
Per NC State Extension, yes. London planetree cultivars 'Bloodgood', 'Columbia', and 'Liberty' show meaningfully better anthracnose resistance than standard American sycamore in head-to-head trials. If planting a new tree in an area with a history of disease pressure, these are worth specifying.
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Sources
- University of Minnesota Extension — Anthracnose of Shade Trees
- Penn State Extension — Sycamore Anthracnose
- Clemson HGIC — Sycamore Anthracnose
- NC State Extension — Sycamore Anthracnose Management
- Cornell Cooperative Extension — Tree Disease Management