There are five species of tent caterpillars in Colorado. Western tent caterpillar, southwestern tent caterpillar, Sonoran tent caterpillar, forest tent caterpillar, and the eastern tent caterpillar are all found in our state. Adult moths are usually brown to reddish brown and can reach 1.5 inches in size.
Their conspicuous tents are where the larvae are found. Different tent caterpillars will feed on various species of trees with fruit trees, aspen, mountain mahogany, oak, ash, and cottonwood used as hosts. Tent caterpillars feed and establish their silky tents in the crotches of trees and shrubs in late spring. It should be noted that fall webworm and tiger moths would also make "tents" as do some other insects.
Physically removing the insects/tents or spraying with Bacillus thuringiensis, spinosad, pyrethrins, or carbaryl can control tent caterpillars. Timing of any spray should correspond with the caterpillars still being present in the tents and on the tree.
For more information, see the following Colorado State University Extension fact sheet(s).
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Updated Tuesday, November 19, 2013