Description of eastern tent caterpillars
Eastern tent caterpillars are dark-colored, slightly fuzzy and with lighter stripes down their sides. They form silvery-gray webs, usually located at the fork of a major branch on a tree or shrub. Click here to see images and videos of caterpillars and their tents.
Life cycle of eastern tent caterpillars
There is only one generation of eastern tent caterpillars each year. The female moth lays egg masses on the branches of host plants during the summer. Eggs do not hatch until the following spring, usually in April, depending on temperature. The caterpillars feed on the host plant foliage for 4 to 6 weeks. During the daytime, the caterpillars feed on buds and foliage. On cloudy, rainy days and at night, the caterpillars remain in the protective confines of the tent. Tents start very small but enlarge as the caterpillars feed and grow and add to the tents, making them more evident in the landscape, orchard, and roadsides.
When the caterpillars are fully grown, they crawl to the ground and pupate in a protected location. Large numbers of wandering caterpillars near homes can cause concern, but they are done feeding, and no management is necessary at this point. Adult moths emerge several weeks later; mate and the female moths lay the egg masses on branches that will hatch the following year
Damage caused by eastern tent caterpillars
Caterpillars feed on buds and foliage a variety of trees and shrubs but prefer apple, crabapple, wild plum, cherry, and similar trees.
Management of eastern tent caterpillars
Damage can be reduced by removing and destroying tents and caterpillars as soon as they are noticed. Tent removal should be done in early morning or late evening or on cool, rainy days when the caterpillars occupy the tents. The caterpillars and the silk webbing are harmless to people; no harm comes from taking down the tent with your bare hands, although many prefer to remove the tent and caterpillars with a paper towel or gloved hands. Foliage sprays of Bacillus thuringiensis or other labeled insecticides can be applied for caterpillar control on ornamentals when the caterpillars are small. Insecticides are generally ineffective against grown caterpillars. Tents that are not discovered until late May can be ignored as the caterpillars have nearly finished feeding and are at their maximum size. If there are no caterpillars present, the tent is old, and no treatment is necessary.
Click here to watch a video from the Dubuque County Extension Office of eastern tent caterpillar removal in the home orchard.
Caterpillars often confused with the eastern tent caterpillar
The eastern tent caterpillar is often confused with other caterpillar species; the forest tent caterpillar, fall webworm, and the bagworm.
The forest tent caterpillar (Malacosoma disstria) is a closely related but different species that occasionally has regional outbreaks with large populations heavily defoliating forested areas. These outbreaks are more common in northeastern Iowa. Forest tent caterpillars do not make tents.
Fall webworms (Hyphantria cunea) are not closely related, but the caterpillars feed as a group and build a silken ‘tent’ or web in trees. Fall webworms make their web around the leaves as they feed, so they are usually at the ends of branches and are larger. Fall webworms are also active much later in the year and are noticed August-September.
The bagworm moth caterpillar (Thyridopteryx ephemeraeformis) lives its entire life inside a tough protective case made of silk and camouflaging bits of foliage. Each caterpillar makes its own bag that it carries around as it feeds with the head and legs sticking out the open, top end of the bag. As the caterpillar eats and grows, the bag is enlarged until by the end of the summer, what started as tiny pods only one-quarter inch long will have grown to almost 2 inches in length.
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