In early spring, they mature and deposit eggs under a fluffy, waxy covering. When eggs hatch in May, nymphs move to the open buds and feed on those tissues. Mature females and the feeding of these nymphs stimulate the development of the gall, which eventually encloses the young adelgids. During early summer, adelgids mature and lay eggs inside galls. When the eggs hatch, each cell in the gall contains several individuals.
Galls become brown and dry.
They crack open in late July or early August, allowing the insects to escape. Winged adults fly to a twig on the same tree or to nearby spruce trees to deposit eggs. Eggs hatch in the fall to establish the overwintering generation. There is one generation each year. The best control is to prune off galls before they open in the summer.