Douglas-fir: Heavy populations can cause yellowing of needles.

Heavy gall production on blue spruce is often related to the presence of both blue spruce and Douglas-fir in close association.

New galls will become obvious as new shoots expand in the spring.

Avoid planting blue spruce in close association with Douglas-fir.

Physical: Prune out individual galls on lightly infested trees. Remove heavily infested trees.

Chemical: Insecticides should be used just as bud breaks. Indiscriminant use of broad spectrum insecticides such as carbaryl on spruce can lead to spider mite outbreaks. Dormant oils can be applied prior to bud expansion.

Dormant oil

On Douglas-fir, no galls are found. The life stage on Douglas-fir appears as a small, white, cottony mass attached to the undersides of needles.

Life history: The life cycle is very complicated. On spruce, females lay eggs in the spring near the terminal bud. Nymphs hatch and feed at the needle bases of expanding buds, this results in a gall forming over them. By mid-summer the galls dry up, open and the adelgids then fly to Douglas-fir to lay eggs. The nymphs overwinter on the Douglas-fir and in the spring they return to spruce. However, they do not need Douglas-fir to complete the cycle.