About the Douglas Fir Adelgid
The gall adelgid (Adelges cooleyi) is an adelgid species that produces galls in spruce trees. They infect the new buds of native spruce trees in the foothills of the Rocky Mountains in the spring. They also attack blue spruce to a lesser degree. The insects complete two generations within the year. They require two different trees for its life cycle, the second being the Rocky Mountain Douglas-fir. They may also attack Sitka, Engelmann, or white spruce. The many different species of adelgids produce different galls on different spruce species.
The Cooley spruce gall adelgid (Adelges cooleyi Gillette) is mainly a western species that usually alternates between white spruce and Douglas fir. It is rare in eastern Canada. In Ontario, the galls are found mostly on Colorado spruce.
The infection is most noticeable on spruce in the spring, May to June, when the galls appear. This infection may be mistakenly diagnosed to be caused by worms, grubs, or even as a sex organ of the spruce. Spruce pollen, however, is released from a smaller structure that lacks needles. The galls are characterized by this pineapple-like form, with a length of 0.5 cm to 8 cm depending on the... Wikipedia →