Spruce Disorder: Spruce Gall Adelgids
Author(s) R. C. Williamson, P. J. Pellitteri.
Tiny aphid-like insects frequently cause unusual swellings called galls at or near the ends of spruce branches. The insects, technically known as adelgids, are often called spruce gall aphids. Their feeding causes galls to form.
Two insect species are involved, the Cooley spruce gall adelgid, Adelges cooleyi, and the eastern spruce gall adelgid, Adelges abietis. Between them they can attack almost all spruce species. White, Colorado blue, Sitca, and Engelmann spruce are the primary hosts of Cooley spruce gall adelgids. Douglas fir is an alternate host for this insect. Eastern spruce gall adelgids attack mainly Norway and white spruce, and occasionally other spruces.
Find out how to identify, prevent, and control spruce gall galls in your spruce trees by reading this helpful fact sheet (2 pages; Revised in 1999).