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Spiny Witchhazel Gall Aphid

Hamamelistes spinosus[3]

The spiny witchhazel gall aphid is an aphid that alternates between witchhazel, where it makes spiny bud galls, and river birch, where it crinkles the leaves.[1][2]

Group
Insect
Order
Hemiptera
Family
Aphididae
US records
32 states
Sources
3 cited
Updated
2026-10-16
Spiny gall on a witchhazel twig made by spiny witchhazel gall aphids
Spiny gall on a witchhazel twig made by spiny witchhazel gall aphids. (c) Jeff Clark, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0
On this page
  1. Identification
  2. Where it lives
  3. Biology
  4. Damage and signs
  5. Health risk
  6. Control
  7. Related profiles
  8. Common questions
  9. Sources

How to identify it

  • On witchhazel it forms spiny galls from the flower buds; on river birch it causes corrugated, bumpy ridges on the leaves.[1][2]
  • The aphids in the corrugated birch galls are the stage people notice most.[1]

Where it lives

Found wherever witchhazel and river birch grow together, including North Carolina and Maryland.[1][2]

US map: public records from 32 states since 1990 (GBIF).

Biology and life cycle

Eggs laid on witchhazel in June and July hatch the next spring; the nymphs feed on flower buds and cause a spiny gall where winged aphids develop.[1]

Winged aphids fly to birch and produce a scale-like generation that overwinters on birch until bud break.[1]

Damage and signs

  • Witchhazel and river birch are its only known hosts.[1]
  • River birch sheds most damaged leaves and grows new ones, so infested trees suffer no lasting harm.[1][2]

Health risk

None to people or pets.[1]

Control

Prevention

Treat the birch galls as cosmetic; they cause no serious injury and really need no treatment.[1]

Pesticides

If galls must be prevented, a landscape aphid insecticide such as imidacloprid applied to birch at bud break in early spring works, but it must be repeated every year.[1]

Common questions

Why are my river birch leaves crinkled and bumpy?
Most likely spiny witchhazel gall aphids; the damage is cosmetic.[1][2]
What is the spiky green thing on my witchhazel?
A gall made by spiny witchhazel gall aphids feeding on the flower bud.[1]

Sources

  1. NC State Extension, “Spiny Witchhazel Gall Aphid (PDIC Factsheet).” content.ces.ncsu.edu/spiny-witchhazel-gall-aphhid (accessed 2026-10-16)
  2. University of Maryland Extension (Home and Garden Information Center), “Spiny Witchhazel Gall Aphid (pest identification images).” extension.umd.edu/resource/spiny-witchhazel-gall-aphid-images (accessed 2026-10-16)
  3. iNaturalist, “Hamamelistes spinosus taxon page (order and family).” www.inaturalist.org/taxa/127421 (accessed 2026-10-06)

Updated 2026-10-16. Built from sourced records. Spot an error? Tell us.