What's eating my sitka spruce?

Sitka Spruce is most seriously damaged by the white pine weevil, which kills the central leader and creates multi-stemmed, crooked trees — a major concern in plantation forestry. Spruce spider mites and green spruce aphid cause foliage damage. Sitka spruce aphid is specific to this species and can cause heavy defoliation in mild coastal winters.

Pale green aphids suck sap from older needles on inner branches through winter and spring in mild climates; needles turn yellow then drop, leaving only current-year growth and producing a thin, sparse canopy Apply insecticidal soap or pyrethrin spray when aphids are active in autumn–spring; introduce or protect natural predators (ladybirds, lacewings); systemic imidacloprid for persistent infestations

Adults lay eggs in the terminal leader; larvae girdle the inner bark; the leader wilts and dies ('shepherd's crook'), causing a forked or multi-stemmed growth form prized in forestry as a serious defect Prune and destroy infested leaders before larvae emerge in midsummer; apply pyrethroid spray to the terminal leader in early spring; repeated pruning can train a new leader if caught early

Needle stippling, bronzing, and webbing on older inner growth; heavy mite pressure causes early needle drop and a yellow-grey tint to the canopy; worst in warm, dry periods Dormant horticultural oil spray before bud break; miticide (bifenazate or abamectin) or insecticidal soap during the growing season; ensure adequate watering in dry summers