Eastern spruce gall adelgid
Adelges abietis (L.) (Hemiptera Adelgidae)
Orientation to pest
Eastern spruce gall adelgid, Adelges abietis (L.), is a pest of the introduced Norway spruce (Picea abies [L.]) and of various native North American spruces, especially white spruce (Picea glauca [Moench]). It is an invasive species believed to be of European origin. Damage is caused by induction of galls on new growth. Adults, which are wingless, deposit their eggs near buds in spring and newly developing needles are stimulated by developing nymphs to become enlarged, fusing into a pineapple-shaped gall, within which nymphs mature. In summer and early fall, the chambers of the gall open and nymphs emerge and transform themselves into winged adults, which lay eggs. These hatch and nymphs overwinter at the base of needles and buds. In spring, when the gall is newly formed, it is light green in color, but after it matures and insects emerge, it dries and turns brown, remaining on the branch as a sign of earlier infestation. Damage results from twig deaths induced by galls, which makes the tree misshapen. Heavily infested trees may die.
Hosts commonly attacked
This adelgid feeds on black (Picea mariana (Mill.) Britton, Sterns & Poggenburg), Norway (Picea abies), white (Picea glauca) spruces.
Distribution in the USA
Eastern spruce gall adelgid occurs widely in the eastern United States from Maine to Tennessee and Illinois, as well as in northern Minnesota, Wisconsin, and Michigan, and adjacent parts of Canada. Localized infestations also occur in parts of Montana, Wyoming, and South Dakota. A map of this distribution is available at http://www.fs.fed.us/nrs/tools/afpe/maps/ESGA.pdf.
Images of eastern spruce gall adelgid
| Figure 1. Close view of living galls of eastern spruce gall adelgid | Figure 2. Living galls of eastern spruce gall adelgid cut in cross section and showing chambers where insects feed | Figure 3. Dead galls of eastern spruce gall adelgid |
| Figure 4. Openings in gall of eastern spruce gall adelgid after insect emergence | Figure 5. Adult of eastern spruce gall adelgid, Adelges abietis |
Important biological control agents related to this pest species
Because damage from this species is not severe, natural enemies have not been imported from the pest's native range into North America for control. Predacious flies have been observed feeding on this adelgid in Europe (the syphid Cnemodon sp.) and, in Turkey, Leucopis species have been recorded feeding on related adelgids, but in general little is known about the natural enemies of this species.
Web links for information on eastern spruce gall adelgid
- Fact Sheet | Forest Invasive Alien Species, Government of Canada
- Fact Sheet | Ohio State University Extension
Articles
- Flaherty, L., D. Quiring, and J. A. Kershaw, Jr. 2010. Post-gall induction performance of Adelges abietis (L.) (Homoptera: Adelgidae) is influenced by clone, shoot length, and density of colonising gallicolae.. Ecological Entomology 35: 9-15.
