Soft-bodied adelgids which feed by sucking plant juices from spruce trees, are so small they are not readily seen. Their feeding on developing plain tissue causes visible formation of com-like or pineapple-like growths, and can deform, stunt, or kill twigs. Trees most likely to be infested are Norway, white, red, black, blue, sitka, and Englemann spruces.
The Eastern spruce gall adelgid produces galls 1/2- to 1-inch long and the Cooley Spruce gall adelgid causes galls 1 to 3 inches in length. These galls are found near the base of new growth on spruces.
Eastern Spruce Gall Adelgid (Adelges abietis (L.)) - Lives during the winter as an immature female, usually located in a crevice at the base of a spruce bud. It begins feeding in early spring and in May deposits a mass of eggs covered with waxy threads. The eggs hatch about the time the shucks break away from the bud and expose the new needles. The newly hatched adelgids crawl into the mass of new needles to feed. The swelling needle bases develop into a compact mass and form the pineapple-shaped gall with many individual cells inhabited by adelgids. In mid-summer, adelgids emerge after the galls split open and dry to a brown color around the deformed needle base. These adelgids lay the eggs producing the individuals that live during the winter.
Cooley Spruce Gall Adelgid (Adelges cooleyi (Gillette)) - Blue spruce is a favored host of this adelgid. The life cycle, with a few exceptions, is similar to that of the Eastern spruce gall adelgid. The winter is spent on spruce or Douglas fir. Injury to Douglas fir appears as a yellowing and kinking of the needles. In heavy infestations, partial or complete needle fall may occur.
