How to Manage Pests

Pests in Gardens and Landscapes

Seasonal development and life cycle—Adelgids

Most adelgid species alternate generations between two different conifers. Adelgids commonly form galls on spruce, which are considered the primary host on which these insects undergo sexual reproduction and overwinter. Pines are the alternate host for Pineus species, and Adelges species feed on Douglas fir, fir, hemlock, or larch as their alternate host.Adelgids on their alternate hosts are recognized by the cottony white or grayish material secreted by colonies of females on the trunk, limbs, cones, twigs, or needles. Heavily infested trees may seem covered with snow. The adelgids themselves are beneath this material.

Most adelgids have a complex life history. The conifer species serving as the primary or secondary host is not known for all adelgids, and some populations apparently don't migrate between hosts. The insects can look different depending on the host, and each species typically has several different kinds of egg-laying adults. Most species overwinter as eggs under cottony masses or as early-stage immatures under bark or bud scales.

Cooley spruce gall adelgid egg
Cooley spruce gall adelgid egg

Cooley spruce gall adelgid nymphs
Cooley spruce gall adelgid nymphs

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