The Cooley spruce gall adelgid is not usually considered an important pest in the 
forest. However, it may be troublesome where spruce and Douglas-fir are growing 
close together. Ornamental spruce and young spruce trees in Christmas tree planta- 
tions are often seriously damaged by excessive numbers of unsightly galls. No galls 
are produced on Douglas-fir but heavy adelgid attacks on this host can cause 
abnormal dropping of foliage. 
The balsam woolly adelgid, Ade/ges piceae (Ratzeburg), an introduced species 
first recorded in North America from Brunswick, Me., in 1908, now occurs in the 
Maritime Provinces, Canada, and the Northeastern States. Infestations also occur 
over much of Newfoundland, in the Gaspé Peninsula of Quebec, in the southern 
Appalachians, in the Pacific Northwest, and in British Columbia. Its hosts are 
balsam and Fraser firs in eastern North America. Full-grown adelgids are roughly 
spherical, about | mm long, and almost invisible to the naked eye. Because of a 
covering of white wax threads, however, they appear conspicuously as dots of white 
“wool” (fig. 27). 
F-519571 
Figure 27.—Infestation of the balsam woolly adelgid, 
Adelges piceae, on trunk of Fraser fir. 
Clusters of amber eggs are deposited in the late spring and early summer; each 
egg is attached to the bark behind the female’s body by a silken thread. Newly 
hatched crawlers form the only motile stage in the life cycle of this insect. When 
suitable feeding sites are found on the surface of the bark, these crawlers insert their 
stylets, become stationary, and turn black except for fringes of white wax plates 
around the edges of the body and down the dorsum. After a period of dormancy 
lasting from 2 to 8 weeks they develop into the second generation. Adults of this 
generation deposit eggs during midsummer. Hatching soon occurs and all stages are 
found until late fal!. The winter is spent as stationary first-stage larvae. In the spring 
these larvae resume activity and reach maturity by the time the buds begin to swell. 
New adults appear by mid-April in the southern Appalachians and in early May in 
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