Pest profile

Woolly Oak Aphids

Stegophylla brevirostris and Diphyllaphis microtrema · Hemiptera: Aphididae[3]

Woolly oak aphids are small native aphids that cover the undersides of oak leaves with white woolly wax and curl new leaves in spring; they are messy but rarely need control.[1][2]

Oak leaf curled by woolly oak aphid feeding
Oak leaf curled by woolly oak aphid feeding. (c) Thomas Koffel, some rights reserved (CC BY) — via iNaturalist, CC BY 4.0

How to identify it

  • Colonies are conspicuous for the large amounts of white woolly wax they produce on leaf undersides; brown droplets of honeydew collect in the wax.[2]
  • The aphids beneath the wax are pale; young nymphs can be pale green and move more than adults.[2]
  • New leaves of red oaks may curl noticeably in spring.[1]

Look-alikes

Look-alikeHow to tell them apart
MealybugsWoolly oak aphid colonies are sometimes mistaken for mealybugs or whiteflies.[2]
WhitefliesWoolly oak aphid colonies are sometimes mistaken for whiteflies.[2]

Where it lives

Both species occur in eastern North America; UF notes Stegophylla brevirostris is a pest only in Florida.[2]

Biology and life cycle

In Florida, all forms are live-bearing females year-round, with no egg-laying or winged forms known there.[2]

Damage and signs

  • Willow, red and live oaks are the most reported hosts; S. brevirostris prefers live oak.[1][2]
  • By the time damage is noticed it is usually too late to correct for that year; insecticides won't uncurl leaves.[1]

Health risk

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

Control

Traps and physical control

On small trees, a strong spray of water from a hose dislodges and drowns many aphids.[1]

Biological control

They are native species with native natural enemies, and in most cases control isn't needed.[2]

Pesticides

Horticultural oils or insecticidal soaps work, but spraying large trees is difficult, expensive and not worth the effort.[1]

Common questions

What is the white fluff under my oak leaves?
Likely woolly oak aphids, which secrete white woolly wax.[1][2]
Do woolly oak aphids hurt oaks?
Usually not enough to need control, though they curl leaves and make a mess.[1][2]
Will spraying uncurl the leaves?
No; by the time curling shows, it is too late for that year.[1]

Sources

  1. NC State Extension, “Woolly Oak Aphids.” content.ces.ncsu.edu/woolly-oak-aphids-1 (accessed 2026-10-15)
  2. University of Florida IFAS Extension (Featured Creatures), “Woolly Oak Aphids (EENY-574).” ask.ifas.ufl.edu/publication/IN1011 (accessed 2026-10-15)
  3. iNaturalist, “Stegophylla taxon page (order and family).” www.inaturalist.org/taxa/454656 (accessed 2026-10-06)

Updated 2026-10-15. Built from sourced records. Spot an error? Tell us.