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Woolly alder aphids: the white fluff drifting through the air in fall

September to October

Some of the small white tufts drifting through the air on warm September and October days are woolly alder aphids, insects wrapped in waxy threads that make them look like floating lint. They are flying from alder shrubs back to their winter host, usually silver maple, where most overwinter as eggs.

Why this time of year

On warm days in September and October the winged autumn generation of woolly alder aphids leaves alder shrubs for silver maple. Shortening daylight, along with crowding, temperature and food quality, triggers that generation.

How to notice it

  1. Watch for tiny white flecks drifting through the air near alder shrubs or silver maples on warm afternoons.
  2. Follow one with your eyes as it drifts on the breeze.
  3. Look closely without touching: under the white wax is a small dark-bodied insect, not a seed or a bit of lint.
  4. Check nearby alder shrubs (often along wet, woodland-edge ground) and silver maple trees for the two plants the aphids are traveling between.

Try this with kids: Can you spot one of the floating fuzz balls and figure out there is a tiny bug hiding under all that white fluff?

overwinter: survive through the cold months until spring

Sources

  • uwm.eduUW-Milwaukee Field Station (2014): woolly alder aphids carry waxy abdominal secretions and drift like bits of fluff, nicknamed 'fairy flies, fluff bugs, and angel bugs'; 'Decreasing day length signals' the winged generation; the return trip is from alder to silver maple, where most overwinter as eggs, though some adults may overwinter. Places the species east of the Mississippi.
  • northernwoodlands.orgNew England forestry/nature magazine article: describes the fall flight occurring 'on warm days' in September and October, with aphids appearing as white 'fuzzballs' sailing on the breeze; winged offspring are produced in response to day length, crowding, temperature, and food quality, and the aphids alternate between alder and silver maple hosts.
  • yardandgarden.extension.iastate.eduIowa State Extension: two-host cycle (alder and silver maple), winged adults with white wax look like 'tiny masses of cotton floating through the air' and have a plump bluish-black body. The flight it describes is the early-summer maple-to-alder flight; cited for APPEARANCE only, not the fall mechanism.

Checked against these sources on September 22, 2026.

In the guide for September, October

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