Elm Leafminer

How to identify it

• Adults are about 3 mm long and look like tiny black wasps or flies; males are rare or absent.^[1][2]
• Larvae are tiny and white with pale brown heads, feeding inside the leaf.^[2]

Look-alikes

Where it lives

Introduced to the United States before 1898; found in New England, North Carolina and elsewhere.^[1][2]

Biology and life cycle

Adults emerge as new elm leaves expand, in May in New England, and insert up to 25 eggs per leaf through slits cut with a saw-like ovipositor.^[1][2]

Grown larvae drop to the soil, so damage is often discovered after they have left.^[2]

Damage and signs

• Blotch mines form between lateral veins and may merge; mined areas brown and may drop out, leaving holes.^[1][2]
• Heavy mining can defoliate trees, though most elms reflush and look fine by late summer; hosts include American, Camperdown, English, Scotch and Siberian elms.^[1][2]

Health risk

None to people or pets.^[1][2]

Control

Traps and physical control

On small trees, pick and destroy mined leaves.^[1][2]

Pesticides

Where it was a problem before, target adults before egg laying or apply a systemic while mines are new; sprays after mid-July don't help.^[1][2]

Related profiles

• Elm Leaf Beetle
• Birch Leafminer
• Woolly Elm Aphid
• Elm Casebearer

Common questions

Why are my elm leaves full of brown blotches in spring?

Elm leafminer larvae feeding between the veins are a common cause.^[1][2]

Sources

1. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Fenusa ulmi (Elm Leafminer).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/fenusa-ulmi (accessed 2026-10-16)
2. NC State Extension, “Elm Leafminer (PDIC Factsheet).” content.ces.ncsu.edu/elm-leafminer (accessed 2026-10-16)
3. iNaturalist, “Fenusa taxon page (order and family).” www.inaturalist.org/taxa/176454 (accessed 2026-10-06)