Eastern Spruce Gall Adelgid
Adelges abietis (Linnaeus)
The eastern spruce gall adelgid is a key pest of Norway spruce, Picea abies , in northeastern United States. Occasionally, it also infests white spruce, P. glauca , red spruce, P. rubens , and Colorado blue spruce, P. pungens . In Pennsylvania it is a pest of plants in landscapes, nurseries, and Christmas tree plantations. In the past, literature referred to this species as an aphid.
This pest overwinters on spruce as female nymphs in bark crevices on the current year's twigs, especially at the bases of buds. In the spring they resume feeding and mature into adults. Females usually start laying eggs about the time buds start to open. Each female lays between 100-200 eggs that normally are laid in small groups. Young nymphs hatch from eggs in 7-10 days and crawl into the bud and among the bud scales. Once in the bud, they begin feeding on the new tissue. Feeding stimulates most plant cells to produce an individual gall where each needle should develop. The result is a series of affected needles, which collectively grow into a stunted pineapple-shaped gall. This species becomes enclosed in spaces between the swollen round needles. They remain there until the galls are fully developed, begin to turn brown, and open from late July through October. During this period of time mature winged individuals fly from galls to lay eggs on host needles. Eggs hatch into young nymphs that overwinter. One generation occurs each year in Pennsylvania.
Fig. 1. Eastern spruce gall adelgid damage.
The galls formed by this pest are short, pineapple-shaped growths (Fig. 1). They are usually less than 25 mm long, green at first, but turn brown when they open and the adults emerge. Eggs are covered with white waxy filaments.
Feeding by this species stimulates the formation of a gall at the base of current year's growth. Infested trees are seldom killed, but the aesthetics of an infested tree may be greatly reduced.
Pruning and destroying green-colored galls during June or July before they open, and therefore, before adults emerge, is practical for light infestations on a few small trees.
Apply horticultural oil according to label directions as a dormant treatment, before new growth starts, when temperatures remain above freezing. Horticultural oil removes the glaucous bloom (blue color) from both Colorado blue spruce and Koster spruce.
To manage overwintering life stages of this pest, apply registered insecticides according to label directions from mid-September through early October. A second alternative is to treat infested plants in April prior to budbreak, before females mature and start laying eggs.
For optimal results be sure to thoroughly cover the bases of buds. Also, the use of certain insecticides may cause outbreaks of spruce spider mite, mainly because of their effect on mite predators. Be sure to monitor for outbreaks of spruce spider mite when using treatment materials that may impact mite predators.
Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.
Authored by: Gregory A. Hoover, Sr. Extension Associate
Penn State College of Agricultural Sciences research, extension, and resident education programs are funded in part by Pennsylvania counties, the Commonwealth of Pennsylvania, and the U.S. Department of Agriculture.
Visit Penn State Extension on the web: http://extension.psu.edu
Where trade names appear, no discrimination is intended, and no endorsement by Penn State Cooperative Extension is implied.
This publication is available in alternative media on request.
The Pennsylvania State University is committed to the policy that all persons shall have equal access to programs, facilities, admission, and employment without regard to personal characteristics not related to ability, performance, or qualifications as determined by University policy or by state or federal authorities. It is the policy of the University to maintain an academic and work environment free of discrimination, including harassment. The Pennsylvania State University prohibits discrimination and harassment against any person because of age, ancestry, color, disability or handicap, national origin, race, religious creed, sex, sexual orientation, gender identity, or veteran status. Discrimination or harassment against faculty, staff, or students will not be tolerated at The Pennsylvania State University. Direct all inquiries regarding the nondiscrimination policy to the Affirmative Action Director, The Pennsylvania State University, 328 Boucke Building, University Park, PA 16802-5901; Tel 814-865-4700/V, 814-863-1150/ TTY.
© The Pennsylvania State University 2013