Pest profile

Cooley Spruce Gall Adelgid

Adelges cooleyi · Hemiptera: Adelgidae[4]

Pineapple- or cone-shaped galls on spruce shoot tips are made by the Cooley spruce gall adelgid, which alternates between spruce and Douglas-fir.[1][2]

Cone-shaped Cooley spruce gall at the tip of a blue spruce shoot
Cone-shaped Cooley spruce gall at the tip of a blue spruce shoot. Photo: Braden J. Judson, public domain (CC0), via iNaturalist

How to identify it

  • Galls form at the tips of new spruce growth, about 1/2 to 4 inches long, green to purple, turning brown as they dry.[1][2]
  • On Douglas-fir, nymphs settle under white, cottony tufts on needles, shoots and cones.[1]
  • Empty galls harden and can persist for years.[1]

Look-alikes

Look-alikeHow to tell them apart
Eastern spruce gall adelgidIt makes smaller 1/2- to 1-inch, pineapple-shaped galls at the base of new shoots and lives on spruce alone.[2]

Where it lives

It feeds on spruce and Douglas-fir; in Minnesota mainly on Colorado blue and white spruce, and in California mostly along the North Coast and in mountains where Douglas-fir is common.[1][2]

US map: public records from 19 states since 1990 (GBIF).

Biology and life cycle

Some populations alternate generations between spruce and Douglas-fir.[1]

Galls form on spruce only when Douglas-fir is nearby, because that host supplies the gall-forming stage.[1]

About midsummer the nymphs leave the galls and molt into winged adults.[1]

Damage and signs

  • Heavy feeding on Douglas-fir distorts and spots needles and makes them drop early.[1]
  • Spruce damage is rare, mainly when young trees carry many galls year after year.[2]

Health risk

It feeds on conifers only; the sources describe no risk to people.[1][2]

Control

Prevention

Control is generally not suggested; most galls don't seriously harm plants.[2]

Traps and physical control

Prune and dispose of galls if they're annoying, before the adelgids leave.[3]

Pesticides

For galling insects that winter on the plant, horticultural oil before spring activity is the timing Minnesota Extension gives.[2]

Common questions

What are the cone-like growths on my blue spruce?
They're probably Cooley spruce galls, formed by the adelgid at shoot tips.[2][1]
Why do I see white fluff on Douglas-fir needles?
Cooley spruce gall adelgid nymphs cover themselves with white cottony tufts on Douglas-fir.[1]

Sources

  1. University of California Statewide IPM Program, “Adelgids (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/adelgids.html (accessed 2026-10-06)
  2. University of Minnesota Extension, “Insect and mite galls (Yard and garden insects).” extension.umn.edu/yard-and-garden-insects/insect-and-mite-galls (accessed 2026-10-06)
  3. University of California Statewide IPM Program, “Gall Makers (Pests in Gardens and Landscapes).” ipm.ucanr.edu/PMG/GARDEN/PLANTS/INVERT/gallmakers.html (accessed 2026-10-06)
  4. iNaturalist, “Adelges cooleyi taxon page (order and family).” www.inaturalist.org/taxa/334163 (accessed 2026-10-06)

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