Key Features
- Green or purplish galls on shoot tips
- Galls 1/2 inch in diameter
- Twisted needles on Douglas fir
Symptoms
This cone-like gall is produced on the tips of new growth of Colorado blue, Sitka and Engelmann spruces in response to feeding by this sucking insect. The gall is green or purplish in color, 1 to 2 inches long, 1/2 to 3/4 inches in diameter and resembles a small pineapple in an early stage of development. Galls turn brown and are easily visible in winter. Galls can't be removed without cutting twig tissue. On Douglas-fir, needles become twisted and yellowed.
Biology
This insect takes two years to complete its life cycle on Douglas-fir and spruce. Winged adults fly from Douglas-fir to spruce in late July. Adults lay eggs on spruce that hatch into nymphs that spend the winter on spruce twigs. Nymphs become active on spruce in early spring just before the buds break. They develop into adults in May that lay eggs on twigs. When these eggs hatch around the time that lilacs bloom, nymphs crawl to the base of spruce needles and cause them to produce the characteristic galls. In mid-summer, galls on spruce open to release winged adults that fly to Douglas-fir where they lay eggs. These eggs hatch into nymphs that overwinter on Douglas-fir. After bud break, nymphs become active and start to distort leaves. They develop into wingless adults in May. These adults produce offspring that become both winged and wingless adults in July. Wingless adults remain on Douglas fir and winged adults fly to spruce to complete the cycle.
Management Recommendations
ON SPRUCE: The presence of old galls on spruce in the winter suggests that infested Douglas-fir are near enough for adelgids to have laid eggs on spruce the previous summer. Apply broad spectrum insecticides to the plant just prior to budbreak to kill nymphs that wintered on the plant as eggs. By killing these nymphs you prevent adults from laying the new generation of eggs on young needles, where galls are formed in late May. Applications of imidacloprid applied in the fall are effective in preventing galls during the spring. ON DOUGLAS FIR: Look for twisted yellow needles with fine wax strands. Apply insecticidal soap or oil to kill nymphs and prevent further twisting. Conventional foliar applied insecticides, or soil applications of imidacloprid or dinotefuran are also effective in the spring. Do not interplant spruce and Douglas fir, since they are alternate hosts of the Cooley spruce gall adelgid.
Effective Pesticides
Active Ingredients include: Acetamiprid, Bifenthrin, Carbaryl, Cyfluthrin, Dinotefuran, Imidacloprid, Insecticidal soap (Potassium salt of fatty acid), Lambda- cyhalothrin, Neem oil
