What's eating my western hemlock?

Western Hemlock is threatened by the western blackheaded budworm and hemlock looper moth, which can cause large-scale defoliation. Hemlock woolly adelgid is an emerging threat on the Pacific coast. Bark beetles attack stressed trees, and deer browse young regeneration. Aerial Bt sprays are used in forest settings during outbreaks.

Larvae mine and web current-year needles in spring; repeated defoliation over 2–3 years causes significant top-kill and growth loss; outbreak populations crash periodically Aerial or ground application of Bt (Bacillus thuringiensis kurstaki) targeting young larvae in spring; spinosad as alternative; single outbreaks rarely kill healthy trees

Caterpillars consume entire needles, causing rapid reddish-brown discoloration and tree death within a single season during severe outbreaks Bt aerial sprays during outbreak years coordinated by forestry agencies; nuclear polyhedrosis virus bioinsecticide where registered; population usually collapses after 2–3 years

White woolly masses at needle bases; gray needles; dieback spreading from lower crown; increasingly recorded on Pacific coast populations Systemic imidacloprid or dinotefuran soil drench for specimen trees; report new infestations to forestry authorities; early detection is critical