Elm leafminer
Fenusa ulmi
8 host plants
Last updated
This profile contains verified pest data from extension databases. Regional field notes and expert review are in progress.
Elm leafminer larvae create winding, serpentine mines within American elm leaves starting in late spring through summer. You will see pale, snaking trails inside the leaf tissue with brown, dead tissue along the mines. Infested leaves become unsightly and may drop prematurely. Damage accumulates through the growing season. The pest is generally minor in home settings, causing appearance issues rather than serious tree decline.
This is primarily a cosmetic problem in landscape settings. Prune out heavily mined branches if appearance is important. No chemical treatment is justified given that trees tolerate leaf loss well. Encourage natural parasitoids that keep leafminer populations in check. Maintain tree vigor through proper watering to promote rapid recovery and regrowth of damaged foliage. Most elms in home gardens show only minor mine damage without any management intervention.
Quick Reference
Elm leafminer Adult emergence typically begins around 1116 GDD₃₂. As of April 23, 2026, all seven Puget Sound stations have passed this threshold (1434.4–1592.7 GDD₃₂), so Adult emergence is likely underway across the lowlands.
Regional Season Tracker
GDD₃₂ accumulation across 7 Puget Sound stations · as of Apr 23, 2026| Station | GDD₃₂ | Current Stage | Next | To Go |
|---|---|---|---|---|
| Issaquah / East King | 1,593 | Adult emergence | — | — |
| Seattle / UW | 1,554 | Adult emergence | — | — |
| Kent / Auburn | 1,537 | Adult emergence | — | — |
| Olympia / Tumwater | 1,505 | Adult emergence | — | — |
| Bellingham / Whatcom | 1,483 | Adult emergence | — | — |
| Tacoma / Puyallup | 1,472 | Adult emergence | — | — |
| Sequim / Rain Shadow | 1,434 | Adult emergence | — | — |
Source: Herms (OSU) phenological tables: 219 GDD₅₀ adult emergence, Secrest Arboretum OH 1997-2001 (Table 4); 228 GDD₅₀ Dow Gardens MI 1985-1989 (Table 3). UMD IPMnet Pest Predictive Calendar corroborates (Gill & Klick, base 50°F, Jan 1 biofix). Updated 2026-04-03. About GDD₃₂ →
Cultural Controls
- Natural predators may help control populations.
- Pinch, or pick and destroy, infested leaves to kill larvae.