Balsam woolly adelgid

Inspect branches and main stems of silver fir and other true firs closely for small cottony white masses clustered on bark; these are colonies of adelgids covered in white waxy material. Heavy infestations can stunt branch growth or cause branch dieback. Swollen knots may form where adelgids feed on young growth in Puget Sound region plantations.

Maintain tree vigor through adequate moisture and wind protection; healthy trees tolerate adelgid feeding better. Prune heavily infested twigs in winter when pests dormant. Horticultural oil applied in March coats overwintering stages and reduces spring populations. Apply insecticidal soap when crawlers are active in spring or early summer. This pest causes more damage in coastal areas.