Douglas-fir Tussock Moth

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.