Elm Anthracnose vs Dutch Elm Disease

Elm anthracnose is a fungal leaf and twig disease that is rarely fatal but can produce dramatic-looking symptoms that worry homeowners into suspecting Dutch Elm Disease. The two conditions are easily distinguished by where the symptoms appear and what they look like.

What elm anthracnose is

Elm anthracnose is caused by Stegophora ulmea (formerly Gnomonia ulmea), a fungus that overwinters in fallen leaves and infected twigs. It primarily attacks leaves and small twigs, producing dark spots, blotches, and shoot dieback. Severe outbreaks can defoliate trees, but the tree itself usually survives — anthracnose does not invade the vascular system the way DED does.

The disease is worst in cool, wet springs that favor fungal sporulation and infection of newly emerging leaves. Hot dry summers stop disease development.

Where they overlap

Both conditions:

Are caused by fungi

Affect elm trees (anthracnose mostly American elm)

Can cause leaves to turn brown

Can cause some branch dieback in severe cases

How to tell them apart

Feature | Dutch Elm Disease | Elm anthracnose
Primary symptoms | Wilting, vascular discoloration | Black/brown leaf spots and blotches; crinkled, distorted leaves
Where damage appears | Branches and canopy structure | Individual leaves (especially newly emerging ones)
Vascular streaking | Yes — chocolate brown | No — wood looks normal
Tree death | Common outcome | Rare — defoliation possible but recovery typical
Worst weather | Warm, dry beetle flight season | Cool, wet springs
Beetles involved | Yes | No
Dieback pattern | Whole branches die | Twig tips die back; trunks unaffected

What anthracnose actually looks like

The classic anthracnose symptoms:

Black or dark brown spots on leaves, often along the midvein and main lateral veins

Crinkled, distorted leaf shape when infection occurs while leaves are still expanding

Premature leaf drop in severe cases — sometimes a tree partially defoliates by midsummer

Twig dieback at the tips (1–3 inches), with small black fruiting bodies visible on dead bark

No vascular discoloration when bark is peeled from a dead twig

Why misdiagnosis matters

Anthracnose generally requires no chemical treatment — most trees recover with good cultural care (fall leaf cleanup, watering during drought, avoiding stress). Treating an anthracnose case as DED would mean spending hundreds to thousands on unnecessary fungicide injections.

Conversely, missing real DED while assuming "it's just anthracnose" wastes the early-detection treatment window. Vascular streaking when bark is peeled rules out anthracnose.

Management for confirmed anthracnose

Rake and dispose of fallen leaves in autumn (removes overwintering fungus)

Prune out dead twigs in winter

Water during dry periods to support recovery

Avoid overhead irrigation that wets foliage

Most modern resistant elm hybrids show some anthracnose tolerance as well

When to suspect anthracnose

Strongly consider anthracnose when:

The damage is mostly leaves, not branches

Spots and blotches are visible on individual leaves

A wet cool spring preceded the symptoms

No beetle activity is evident

The tree has been showing the same pattern for multiple springs without significant decline

Related pages

Differential Diagnosis Guide

What Are the Symptoms of Dutch Elm Disease?

What are Dutch Elm trees?

Dutch Elm Disease Symptom Checker

References

Sinclair, W. A., & Lyon, H. H. (2005). Diseases of Trees and Shrubs (2nd ed.). Cornell University Press.

Stipes, R. J., & Campana, R. J. (Eds.) (1981). Compendium of Elm Diseases. American Phytopathological Society.

Walker, J. (1980). "Gnomonia ulmea on elms." Mycological Papers, 142, 1–24.