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. If you see vascular streaking when peeling bark, it is not 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

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.