Adelgids

Immatures (nymphs) of the Hemlock Woolly Adelgid on the stem of a Canada Hemlock.
The "woolly masses" created by the Pine Bark adelgid, on an Eastern White Pine.
Galls formed on blue spruce by the Cooley Spruce Gall Adelgid.

Adelgids are small, aphid-like insects that are always associated with conifers. At one time, they were considered to be aphids but now are in their own family (adelgidae) within the insect order Homoptera. They are most closely related to the woolly aphids (Eriosomatidae) and the Phylloxeran aphids (Phylloxeridae). Both of these aphid groups have members that are associated with producing wax and galls; they also have very short or no cornicles.

Adelgids, along with being associated with conifers, are also known for producing woolly masses and/or galls on the host plant. They may feed on needles, stems, through the bark or within galls, depending on the species and the host plant involved. Many adelgid species have alternate host plants where specific life stages develop. For the gall-inducing species, the galls will only be found on one of the two alternate hosts. Their potential damage can range from being only an aesthetic nuisance to that of killing the host plant; this depends on the specific adelgid pest and the host plant involved.

Written by: Robert Childs
Revised: 10/2011