Douglas-fir Tussock Moth

    Douglas-fir Tussock Moth

    Orgyia pseudotsugata

    douglas-fir tussock moth

    Adult Douglas-fir tussock moth and pupal case (William M. Ciesla, Forest Health Management International,

    Douglas-fir tussock moth larva

    Douglas-fir tussock moth larva (Donald Owen, California Department of Forestry and Fire Protection,

    Douglas-fir tussock moth damage

    Douglas-fir tussock moth damage (Forest Service Region 2 - Rocky Mountain Region,


    Pest Description

    • adults: wingspan 1 – 2 inches
    • larvae: ~ 1 2/5 inches long; black body with prominent, colorful tufts of hair
    • pupae: ~ 1 inch long; brown and mixed with hairs; located on or near the host tree
    • eggs: laid in masses near pupal cases and covered with hairs from the female

    Host Plants, Diet & Damage

    • spruce, Douglas-fir, true firs
    • feed on new foliage, then older foliage causing brown branch tips
    • damage is typically focused on the top of the tree (do not confuse with Ips beetle damage)
    • larvae can defoliate branches, killing part or all of the tree

    Biology, Life Cycle & Damaging Life Stage

    • overwinter as egg masses on host trees
    • eggs hatch around mid- to late-May
    • larvae migrate or are wind dispersed to new trees
    • larvae feed on new needles and later on older needles
    • full grown larvae pupate on or around the host tree starting around mid-July to early-August
    • adult males fly in late-July to mid-August
    • one generation per year in Utah
    • larvae are the damaging stage

    IPM Recommendations

    • Manage trees to improve or maintain overall health.
    • Monitor trees for egg masses in early spring.
    • Monitor starting in mid-May for egg hatch and larvae.
    • Apply an insecticide (Bacillus thuringiensis var. kurstaki; carbamate; diacylhydrazine; pyrethroid) to newly expanded foliage targeting larvae when they are small.