Hemlock scale

Hemlock scale insects appear as small, flat, brownish oval bumps covering the needles and twigs of spruce and other conifers throughout Western Washington. The scales settle in dense populations, giving infested areas a bumpy, crusty appearance. Heavy infestations cause needle yellowing, branch dieback, and reduced growth vigor, particularly in young landscape plantings. You identify them by their immobile appearance and textured surface.

Apply dormant oil in late winter or early spring to smother overwintering scale. For growing-season populations, horticultural oil targets the crawler stage in early summer. Maintain tree vigor with appropriate watering and avoid stress. Prune out severely infested branches. For high-value trees, a second oil application in mid-summer targets new generations; timing is critical.