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Woolly Beech Aphid

Phyllaphis fagi[3]

The woolly beech aphid is a European aphid that feeds in white, waxy colonies on the leaves of European beech and its cultivars.[1][2]

Group
Insect
Order
Hemiptera
Family
Aphididae
US records
14 states
Sources
3 cited
Updated
2026-10-16
Woolly beech aphids covered in white wax on the underside of a beech leaf
Woolly beech aphids covered in white wax on the underside of a beech leaf. (c) Jenni Ly, 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

  • Wingless females are pale green and 2.0 to 3.2 mm long, covered with white waxy wool; winged females are darker and also woolly.[1]
  • Colonies crowd the undersides of leaves among many shed skins, and the wax gives leaves and anything below a white coating.[1][2]

Look-alikes

Look-alikeHow to tell them apart
Beech blight aphidFound only on the stems of American beech, where colonies wave their rear ends in unison when disturbed.[1]

Where it lives

Native to Europe; found throughout the Northeast wherever European beech is grown, and also introduced to New Zealand, Australia, China and Korea.[1]

US map: public records from 14 states since 1990 (GBIF).

Biology and life cycle

Eggs spend the winter in bark crevices near buds and hatch around budbreak; several generations follow, with activity peaking around mid-June.[1]

Feeding colonies excrete sticky honeydew, which grows black sooty mold and draws ants, bees and wasps.[1][2]

Damage and signs

  • Leaves cup downward on either side of the midvein around the colonies.[1]
  • It feeds only on European beech and its cultivars; it does not infest American beech.[1]
  • Even large populations in back-to-back years do little harm to the tree.[1][2]

Health risk

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

Control

Traps and physical control

A strong stream of water from a hose can wash colonies off the leaves without harming the natural enemies that keep them in check.[1]

Biological control

Lady beetles and other natural enemies likely feed on it in North America.[1]

Pesticides

Sprays are seldom warranted, and the wax and curled leaves make cover sprays less effective; Utah State lists a spring systemic insecticide where treatment is wanted.[1][2]

Common questions

What is the white fuzz under my beech leaves?
On European beech, most likely woolly beech aphids.[1][2]
Does the woolly beech aphid attack American beech?
No. It feeds on European beech and its cultivars only.[1]

Sources

  1. UMass Extension Landscape, Nursery and Urban Forestry Program (Landscape Insect & Mite Guide), “Phyllaphis fagi (Woolly Beech Leaf Aphid).” www.umass.edu/agriculture-food-environment/landscape/publications-resources/insect-mite-guide/phyllaphis-fagi (accessed 2026-10-16)
  2. Utah State University Extension (Integrated Pest Management), “Leafcurl Ash, Woolly Apple and Woolly Beech Aphids (Ornamental Pest Guide).” extension.usu.edu/planthealth/ipm/ornamental-pest-guide/arthopods/aphids-adelgids/leafcurl-ash-woolly-apple-woolly-beech-aphids.php (accessed 2026-10-16)
  3. iNaturalist, “Phyllaphis fagi taxon page (order and family).” www.inaturalist.org/taxa/142754 (accessed 2026-10-06)

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