Pest profile

Woolly Apple Aphid

Eriosoma lanigerum · Hemiptera: Aphididae[2]

Fluffy white wax on apple bark and pruning wounds usually means woolly apple aphid; the real harm comes from galls they cause on roots.[1]

White, cottony wax masses of woolly apple aphid colonies on apple tree bark
White, cottony wax masses of woolly apple aphid colonies on apple tree bark. (c) Mike Bowie, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Colonies hide under white wax in bark cracks, wounds, pruning cuts and leaf axils.[1]
  • The aphids are brown, reddish or purple, 1/20 to 1/10 inch long, with short antennae and barely visible cornicles.[1]
  • Feeding raises globular, warty galls on branches, trunks and roots.[1]

Look-alikes

Look-alikeHow to tell them apart
Mealybugs and whitefliesSome mealybugs and whiteflies also produce white wax; check for the aphids and warty bark galls underneath.[1]

Where it lives

It feeds on apple, cotoneaster and pyracantha, less often hawthorn and pear, and is especially a problem on apples in coastal areas.[1]

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

Biology and life cycle

It sucks phloem sap from limbs, shoots, trunks, leaf axils and roots on first- and second-year wood.[1]

Aphids that overwinter above ground lack wax and are hard to see on bark.[1]

Damage and signs

  • Above-ground galls look bad but matter little; root galls stunt trees and can kill heavily infested young apples.[1]
  • Some varieties get infested at the calyx end of the fruit.[1]

Health risk

It feeds on plants only; UC IPM mentions no risk to people.[1]

Control

Prevention

Where it's a serious problem on apples, consider trees on resistant rootstocks such as M106 or M111.[1]

Biological control

The wasp Aphelinus mali can completely control above-ground colonies if broad-spectrum insecticides aren't used; parasitized aphids turn into black mummies.[1]

Pesticides

Horticultural oil or insecticidal soap give partial control; UC IPM lists acetamiprid or imidacloprid only after petal fall to protect bees.[1]

Common questions

What is the white fuzz on my apple tree bark?
Likely woolly apple aphid colonies hidden under their own white wax.[1]
Do the bark galls hurt the tree?
Not much above ground; root galls are what stunt and sometimes kill young trees.[1]

Sources

  1. University of California Statewide IPM Program, “Woolly Apple Aphid (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/FRUIT/PESTS/woolyapaph.html (accessed 2026-10-06)
  2. iNaturalist, “Eriosoma lanigerum taxon page (order and family).” www.inaturalist.org/taxa/360308 (accessed 2026-10-06)

Updated 2026-10-14. Built from sourced records. Spot an error? Tell us.