The Cooley gall adelgid is a problem in Douglas fir Christmas tree plantations especially when the two host species, spruce primary host and Douglas fir alternate host are planted close to one another. The galls, which are caused by feeding of the nymphs immature adelgids on needles, occur only on spruce. Winged adult females emerge from galls and migrate to Douglas fir if it is present. The next generation nymphs feed on Douglas fir causing yellowing and kinking of the needles; and in cases of heavy infestation, partial or nearly complete needle fall. Damage is most severe in Christmas tree plantations where aesthetic value is reduced by the presence of the unsightly galls on spruces and by the twisting and yellowing of the Douglas fir needles.
Christmas tree (Spruce)-Cooley spruce gall adelgid | Pacific Northwest Pest Management Handbooks
Skip to content Ontario. Green, pineapple shaped galls found at the base of shoots of the current season's growth from spring to summer. In late summer, galls open and turn brown. Often the tips of infested branches are dead, especially if the plant is heavily infested. Norway spruce, Picea abies; Colorado spruce, P.