What Are the Symptoms of Dutch Elm Disease?

Dutch Elm Disease symptoms can vary depending on the strain of fungus and environmental conditions, but several key indicators help identify this tree disease. For visual guidance on disease appearance, see How Does Dutch Elm Disease Look Like?

Primary Symptoms

Wilting and Yellowing (Flagging)

Early indicator: Individual branches show yellowing leaves while the rest of the tree appears healthy

Pattern: Usually starts on one side of the tree or in the upper canopy

Progression: Affected leaves wilt, turn yellow, then brown

Timing: Most commonly observed in late spring to early summer

Branch Dieback

Dead branches: Branches begin dying from the tips inward

Leaf retention: Dead leaves often remain attached to branches

Brittle wood: Affected branches become dry and brittle

Progressive: Spreads to adjacent branches over time

Advanced Symptoms

Vascular Discoloration

Brown streaking: Dark brown to black streaks visible in the sapwood when branches are cut

Ring pattern: Discoloration may form complete or partial rings in cross-sections

Location: Most visible in the current year's growth and outer wood rings

Confirmation: This internal staining is a definitive diagnostic feature

Rapid Tree Decline

Acute form: Tree may die within weeks of first symptoms

Chronic form: Gradual decline over 1-2 growing seasons

Whole tree impact: Eventually affects the entire tree canopy

Seasonal Symptom Patterns

Spring Symptoms

New leaves may be smaller than normal or fail to emerge

Early wilting of new growth

Sparse foliage development

Summer Symptoms

Classic flagging becomes most apparent

Progressive branch dieback

Increased leaf drop

Fall/Winter Symptoms

Dead branches become more visible

Bark may begin peeling from dead sections

Overall tree structure deterioration

Two Forms of the Disease

Acute Form

Rapid onset: Symptoms appear suddenly and progress quickly

Severe wilting: Large portions of the tree affected simultaneously

Quick death: Tree typically dies within the same growing season

Common cause: Usually caused by Ophiostoma novo-ulmi

Chronic Form

Gradual progression: Symptoms develop slowly over multiple seasons

Branch-by-branch: Disease spreads gradually through the tree

Extended decline: Tree may survive 2-3 years with proper care

Common cause: Often caused by Ophiostoma ulmi

Additional Signs

Bark Beetle Activity

Entry holes: Small round holes in bark from elm bark beetles

Galleries: Zigzag tunneling patterns under bark

Sawdust: Fine debris around beetle holes

Connection: Beetles are primary disease vectors

Secondary Effects

Epicormic growth: Shoots may emerge from trunk or main branches

Root sprouting: New growth from root system as tree attempts survival

Increased susceptibility: Weakened trees become prone to other diseases

Diagnostic Considerations

Look-Alike Conditions

Drought stress: Can cause similar wilting patterns

Other fungal diseases: Verticillium wilt has similar symptoms

Construction damage: Root damage can mimic disease symptoms

Chemical injury: Herbicide damage may cause branch dieback

Professional Confirmation

Laboratory testing is often needed to confirm Dutch Elm Disease:

Wood samples: Testing for fungal spores

Microscopic examination: Identifying specific fungal structures

Culture tests: Growing fungus in laboratory conditions

When to Seek Help

Professional consultation with a certified arborist or plant pathologist is warranted when the following are observed:

Sudden wilting of elm branches during growing season

Brown streaking in elm wood

Progressive branch dieback

Any combination of the above symptoms

Early detection and professional diagnosis are crucial for effective disease management and to prevent spread to nearby elm trees. For suspected Dutch Elm Disease cases, see Who Should I Contact if I See Dutch Elm Disease? for reporting guidance.

Related Information:

Disease basics: What is Dutch Elm Disease?

Disease causes: What Causes Dutch Elm Disease?

Internal disease spread: How Does Dutch Elm Disease Spread in a Tree?

Treatment options: Can Dutch Elm Disease Be Treated?