Pest profile

Western Spruce Budworm

Choristoneura occidentalis (also listed as C. freemani) · Lepidoptera: Tortricidae[2]

Western spruce budworm caterpillars feed on the buds and needles of firs, spruce and Douglas-fir, tying shoot tips together with webbing.[1]

Western spruce budworm moth, mottled orange-brown, resting on a pale surface
Western spruce budworm moth, mottled orange-brown, resting on a pale surface. Photo: Ellyne Geurts, public domain (CC0), via iNaturalist

How to identify it

  • Moths are mottled orange-brown with a wingspan of up to 1 inch.[1]
  • Larvae are green to brown with a darker head and, when older, white bumps; grown larvae reach about 1 inch.[1]
  • Eggs are light green, laid in shingle-like masses under needles in mid-July, and make the needle look thicker.[1]

Where it lives

It's mainly a pest of balsam and subalpine firs and also attacks nearby spruce and Douglas-fir; the PNW handbook calls it a significant forest pest but an infrequent landscape one.[1]

US map: public records from 8 states since 1990 (GBIF).

Biology and life cycle

Larvae overwinter in small silk cocoons that are hard to find.[1]

In spring they emerge and spin long silk threads that help them disperse.[1]

Damage and signs

  • Larvae feed on buds and foliage and may tie shoot tips together with webbing into a nest.[1]

Health risk

It feeds on plants; the PNW Insect Management Handbook mentions no risk to people.[1]

Control

Traps and physical control

Hand-pick and destroy larvae when you find them.[1]

Biological control

Parasitoids, predators and bad weather all help keep budworm numbers in check.[1]

Common questions

What is webbing the new shoots of my fir together?
Western spruce budworm larvae tie shoot tips together with webbing as they feed.[1]
Is western spruce budworm a threat to landscape trees?
It's an infrequent landscape pest, though a significant one in forests.[1]

Sources

  1. Pacific Northwest Pest Management Handbooks (OSU, WSU, University of Idaho), “Fir (Abies): Spruce budworm (western) (Insect Management Handbook).” pnwhandbooks.org/insect/hort/landscape/hosts-pests-landscape-plants/fir-abies-spruce-budworm-western (accessed 2026-10-06)
  2. iNaturalist, “Choristoneura occidentalis taxon page (order and family).” www.inaturalist.org/taxa/1430395 (accessed 2026-10-06)

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