Adelgids are an insect with a sucking mouth that feeds on spruce trees and weakens them. Their infestation causes the plant tissue to form cone-shaped galls and disfigure the trees. The female lays her eggs in the crevices of the branch in late spring and they hatch when the new needles are exposed. The new needles provide the adelgid nymphs a plentiful food supply and they form the galls where they live until they emerge in the fall and winter in the tree. They attack a number of trees including blue spruce, white spruce, Colorado spruce, and Douglas fir.
Symptoms: In May and June the galls appear in their characteristic pineapple shape and may be pink, red or even purple in color.
More information: University of New Hampshire Cooperative Extension