Western Tent Caterpillar Update

Damage

Western tent caterpillars feed on most species of deciduous trees and shrubs. If you see tents present on conifers, in spring, chances are good that those are the caterpillars of the silver-spotted tiger moth. Western tent caterpillars feed on most species of deciduous trees and shrubs including: alder, apple, ash, birch, cherry, cottonwood, willow, roses and other fruit trees.

Like the silver-spotted tiger moth, the western tent caterpillar usually causes aesthetic damage to trees. The tent and denuded branch can appear unsightly to many people. Rarely is there more than one tent per established tree. However, on small trees, a single tent can result in 20% defoliation. Larger trees can tolerate this damage. Healthy trees will rebound from the damage. High infestations for multiple years in a row can cause a tree's health to decline. Every now and then, we do have tent caterpillar outbreaks. These outbreaks are cyclical and generally regulated by weather and temperature.

Young ornamental cherry tree defoliated by high populations of Western tent caterpillars. Successive years of this severe defoliation may weaken this young tree's health.