PestControlBasics
Menu

Identify

Treat

Local

About

Elm cockscomb gall aphid

Colopha ulmicola[4]

The elm cockscomb gall aphid makes irregular, ridged galls that jut from elm leaves like a rooster's comb; it spends spring in the galls and summer on grass roots, and the galls don't significantly affect the tree.[1][2][3]

Group
Insect
Order
Hemiptera
Family
Aphididae
US records
34 states
Sources
4 cited
Updated
2026-10-19
Elm cockscomb gall rising from an elm leaf, a ridged, comb-like growth shading from green to red
Elm cockscomb gall rising from an elm leaf, a ridged, comb-like growth shading from green to red. (c) Eli Talhouk, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Look-alikes
  3. Where it lives
  4. Biology
  5. Damage and signs
  6. Health risk
  7. Control
  8. Related profiles
  9. Common questions
  10. Sources

How to identify it

  • Galls are irregular, red-brown, toothed, comb-like growths that jut from the leaf surface.[1][3]
  • On the underside of the leaf each gall has a long seam; split a fresh gall there and you may find a female aphid and her pale white young with dark legs and antennae.[1]

Look-alikes

Look-alikeHow to tell them apart
Elm sack gall aphidTetraneura ulmi, also called the elm-grass root aphid, makes pouch-like sack galls on elm leaves rather than ridged cockscombs, though it also moves to grass roots in summer.[2]

Where it lives

It occurs on native elms, mainly American elm and red or slippery elm, where galls are especially common, and Extension services from Massachusetts and Ohio to Virginia describe it.[1][2][3]

US map: public records from 34 states since 1990 (GBIF).

Biology and life cycle

Elm is the spring host: aphids feed in the leaf galls, and by early summer winged aphids leave the galls and fly to grasses.[1][2]

On the grasses their offspring feed on the roots through summer.[2][3]

In fall, winged aphids return to elm, and their offspring spend the winter on the tree, in bark crevices or as eggs around the buds.[2][1]

Damage and signs

  • The galls are mainly an aesthetic problem and don't significantly affect the overall health of the tree.[1][2]

Health risk

It feeds only on elm leaves and grass roots; UMass, Ohio State and Virginia Extension mention no risk to people.[1][2][3]

Control

Prevention

Management is often unnecessary, since the galls are cosmetic and the aphids leave the elm by early summer.[1][2]

Common questions

What are the red, comb-shaped growths on my elm leaves?
Elm cockscomb galls, made by an aphid that feeds inside them in spring before moving to grass roots.[1][3]
Do elm cockscomb galls hurt the tree?
No. They look odd but don't significantly affect the tree's health, so treatment is usually unnecessary.[1][2]

Sources

  1. UMass Extension Landscape, Nursery and Urban Forestry Program, “Colopha ulmicola, Elm Cockscomb Gall Aphid (Insect & Mite Guide).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/colopha-ulmicola (accessed 2026-10-19)
  2. Ohio State University Extension, “Aphid Galls Rising on Elms (Buckeye Yard & Garden onLine).” bygl.osu.edu/node/1586 (accessed 2026-10-19)
  3. Virginia Cooperative Extension, “Gall-making insects and mites, ENTO-506.” pubs.ext.vt.edu/ENTO/ENTO-146/ENTO-146.html (accessed 2026-10-19)
  4. iNaturalist, “Colopha ulmicola taxon page (order and family).” www.inaturalist.org/taxa/332245 (accessed 2026-10-06)

Updated 2026-10-19. Built from sourced records. Spot an error? Tell us.