Eastern spruce gall adelgidDo your spruce trees have green and/ or brown pineapple-shaped galls 3/4 to 1 inch long at the bases of this and last year's needles? The eastern spruce gall adelgid is the insect whose feeding activities causes these abnormal growths which have needles that are 1/3 normal length, or longer. The galls weaken stems so that they more readily break from weight of snow or other physical stress. The galls also detract from the beauty and symmetry of ornamental spruces.
This adelgid overwinters near end buds as partially grown females called nymphs or stem mothers, and they mature into egg-laying females the next spring. When the new buds are ready to break (form visible needles), eggs are laid at the bud bases and surrounded by a coat of white wooly wax. They hatch within ten days, and the nymphs begin feeding on emerging needles. They move to the needle bases, and their continued feeding causes abnormal and rapid growth and subsequent development of the pineapple-shaped gall. Inside each gall as many cavities where the nymphs, still covered by wooly wax threads, feed and remain entirely protected from parasites, predators, and unfavorable weather. The galls crack open from late July to late September, and the nearly mature nymphs crawl out, settle on needles, cast their nymphal ?skins?, and transform into winged, egg-laying females. These females lay their eggs in unprotected masses near the tips of needles. When these eggs hatch, the young nymphs or stem mothers attach themselves to terminal twigs near dormant buds to spend the winter, and then mature into egg-laying females the next spring when the buds are about to break. Horticulturists and forestry scientists have observed what appears to be resistance to this gall maker. A 5-year study provided some evidence that the ratio of galled to gall-free trees approaches 1:1. Future research will likely result in the marketing of resistant clones of spruce.
An excellent method to control this pest on smaller spruce trees is
to remove and destroy the green galls in early July, before they turn red
and open. This prevents the larvae from maturing into adults and
laying eggs. If chemical control of this pest is contemplated because
of tree size or numbers of trees, the systemic insecticide, acephate, can
be applied just before the buds begin to swell (early April or later for
more northerly locations), and again when the galls are opening (late July
to late September).