How to Manage Pests

Pests in Gardens and Landscapes

Adelgids

Adelgids are small, dark, soft-bodied insects, somewhat pearshaped like aphids.

Identification of species | Life cycle

Damage

Adelgids produce white cottony tufts on the bark, branches, twigs, needles, or cones of their host plants. Cone-shaped galls or swollen twigs may also appear on infested spruce or fir. High populations can cause yellowing, early drop of needles, drooping and dieback of terminals, and can retard or kill trees. Vigorous plants tolerate moderate adelgid populations.

Solutions

Adelgid galls on spruce are usually harmless and can be ignored unless the trees are young or galls become very abundant. To restore the plant's aesthetic quality and provide some control, clip and dispose of infested foliage when the galls are green and before the insects have emerged. Avoid excess fertilization and quick-release formulations, which can promote adelgid populations. Replace some spruce with other tree species to reduce adelgid populations that alternate hosts. Predators may provide some control. A forceful stream of water directed at the cottony masses on conifers, especially on trunks, dislodges and kills many adelgids. High populations, especially on young trees, can be controlled by applying narrow-range oil (but it will discolor spruce foliage) or another broad-spectrum insecticide in the spring when crawlers are abundant.

Cooley spruce gall adelgid adult
Cooley spruce gall adelgid adult

Whitish, waxy material
Whitish, waxy material and stunting of pine needles caused by pine needle adelgid


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