Adelgids feed by sucking plant sap and cause characteristic cone-like growths or galls on spruces. Damage first occurs in late May when the new growth of the branch tips form into cone-shaped galls. The galls are green at first but later turn a reddish-purple color. The old galls dry out and turn a reddish-brown color and may remain on the branches for several years. By the time the galls turn brown, the adelgids have left.