In the fall, the immature female adelgid, small, globular, and wingless (1.2-1.7 mm), finds a spruce on which to overwinter.

The nymphs are light brown when first hatched, becoming black when settled in gall chamber; they are flattened oval in shape and secrete a fringe of white wax.

The lifecycle of the gall adelgid requires six generations to complete, only two of which cause damage (nymph stages) and has two migration phases between the spruce and the Douglas fir.

On Douglas fir, adults are about 0.1 cm long, oval, and light to dark brown in colour.

By midsummer (August to September), the galls begin to dry out, the chambers open and winged forms of the adelgids emerge.

The gall portion of partial infections dies, while the uninfected segment can continue growth, resulting in curved and convoluted shapes.

Severely infested foliage may be completely chlorotic and drop prematurely.1 Late in the summer, some of the woolly adelgids develop wings and fly back to spruce to deposit eggs, which produce the overwintering population.

Others are wingless and remain on Douglas fir trees, where they produce other overwintering forms.2 Natural predators, such as ladybirds/ladybugs, hoverfly and lacewing larvae, spiders, and mites do reduce adelgid and aphid populations to some degree.4 Spraying against these adelgids with chemicals is possible, and can be done in either the fall or the early spring.

Foliar treatments of carbaryl (Sevin) and permethrin have been most effective in Colorado State University trials.