Photos The Cooley spruce gall adelgid is a species of aphid that colonizes various spruces across Canada, but is most abundant in the west. In the Prairie Provinces its primary hosts are white, Engelmann, and blue spruces. Douglas-fir is an alternate host when growing in the same stands as spruce. The cooley spruce gall adelgid has a very complex life cycle which is not fully understood. Adelgids are a small group of insects that are closely related to aphids. The normal life cycle of this adelgid consists of six different forms of the insect over a two-year period on two hosts; spruce and Douglas fir.
These hatch to give young fundatrices which overwinter on the spruce buds. The cooley spruce gall adelgid typically has a two year life cycle alternating between spruce (Picea sitchensis, Picea pungens, Picea engelmannii) and Douglas fir (Pseudotsuga menziesii, Pseudotsuga macrocarpa). The Adelges abietis gall on spruce, known as a 'pineapple gall', (see first picture below) is ellipsoidal with its length less than times the width and usually about mm in length. The spruce needles on the gall are shorter than normal and are a slightly paler green than on a .
Two species of small, soft-bodied insects infest spruce species during the course of rather complicated life cycles. These aphid-like insects called adelgids, produce galls that can disfigure and even kill their hosts. The two adelgids that can be found in the Chicago region are the eastern spruce gall adelgid (Adelges abietis) and the Cooley spruce gall adelgid (Adelges cooleyi). Apr 17, · Most spruce trees are damaged by one of two species of adelgids: the Eastern spruce gall adelgid (Adelges abietis) and the Cooley spruce gall adelgid (Adelges cooleyi).With their sucking mouth-parts, these adelgids feed on plant juices, causing an irritation that results in plant tissue developing into cone-like galls characteristic in form and shape for the aphid .
The Cooley gall adelgid overwinters as a nymph. In the spring female adults deposit eggs under white, cottony wax near the terminal buds on spruce branches. The eggs hatch and the nymphs move to the expanding new growth. Their feeding activity at the base of new spruce shoots causes an elongate, cone-like gall in a matter of a few days.