How to Manage Pests

Pests in Gardens and Landscapes

Pest identification and confirmation—Adelgids

There are about 14 adelgid species in the U.S. in two genera, Pineus and Adelges.

White material on pine
White material on pine

Pine bark adelgids Pineus spp.

Most pine bark adelgids form harmless but sometimes unsightly galls on spruce. Their alternate hosts are pine, or pine and spruce. Adult females are purplish black, soft-bodied insects. Females and yellowish pink masses of eggs occur in cottony, wax-covered colonies on pine. Crawlers resemble tiny pepper grains on the cottony egg masses. The adelgids overwinter as eggs and have several generations a year.

Damage to Douglas fir
Damage to Douglas fir

Cooley spruce gall adelgid Adelges cooleyi

The Cooley spruce gall adelgid alternates generations between spruce and Douglas fir. Their life cycle is completed in two years. Nymphs on spruce overwinter under bark or buds and move to the base of needles in the spring and suck plant juices. This initiates the formation of a light green to purple gall. About midsummer the nymphs emerge from the galls and molt into winged adults. The adults feed and reproduce on spruce or migrate to Douglas fir. They give birth to wingless nymphs. This generation overwinters on Douglas fir. Some of these adelgids develop wings and migrate back to spruce. There the migrants produce males and females that mate, and the females lay eggs.

Statewide IPM Program, Agriculture and Natural Resources, University of California
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