Most recently reviewed by: Tyler Mays & Danielle Sekula (2021)
Common Name(s): Eastern tent caterpillar
The eastern tent caterpillar is a pest that attacks several species of trees, producing webs or tents. The larvae are hairy with oval blue spots on the side, black-brown and yellow-orange markings, with a distinctive white stripe down its back. The adult moths have a one inch wingspan and are reddish-brown with two diagonal stripes down its forewing.
The eastern tent caterpillars form unsightly webs in the fork of branches. The tents are small at first but increase in size and often become eye sores. Healthy trees can generally tolerate feeding from eastern tent caterpillars. Trees that are unhealthy, stressed, or young are more susceptible and may suffer more damage.
The eastern tent caterpillar nests are often mistaken for fall webworm nests, which are located at the ends of the branches. The eastern tent caterpillar is native to North America. They can be found in the U.S. east of the Rocky Mountains, and in Canada from Nova Scotia to Alberta.
Habitat & Hosts
The eastern tent caterpillar attacks a variety of trees, including ornamental and fruit. They prefer cherry, plum, peach, apple, hawthorn, and related plants. They can sometimes be found feeding on oak.
In late spring or early summer, female moths deposit egg masses on small twigs or tree branches. The egg masses contain 150-400 eggs. The females use spumaline, a sticky, frothy substance that is used as an adhesive to attach the eggs to the twigs or bark. The spumaline also covers the egg masses to protect them with a hard covering.
The larvae or caterpillars hatch from the eggs in early spring about the time the leaves on their host plant emerge. The caterpillars will start feeding on the leaves and within a few days start to form webs. The webs enlarge as they grow and provide protection for the caterpillars at night, during the heat, and during rainy spells. The larvae move from the tent to feed, so damage on the tree can be far away from the webs. Defoliation is often concentrated because eastern tent caterpillars feed in groups.
As the larvae grow, they molt or shed their skin several times. During the growth stages, or instars, the caterpillars grow from 1/4 inch to about 2 inches. The color of the caterpillar can also change when it’s growing.
The eastern tent caterpillar has one generation per year. Adult moths only live for a few days.
ManagementIf you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.
Management of eastern tent caterpillars depends on a few factors such as the amount of defoliation, size of webs present, and the nuisance the caterpillars cause. For the best control, you may need to combine cultural and chemical techniques. Prevention and early control are extremely important when it comes to controlling eastern tent caterpillars.
The removal and destruction of egg masses during winter pruning is important to reduce eastern tent caterpillar problems. Normal pruning often removes the caterpillar eggs before they hatch. You should prune twigs containing webs in the spring when you first start to notice the webs. Small webs can be physically removed by hand, while larger tents can be destroyed by a high-pressure water spray or using a long pole.
Natural enemies play an important role in controlling eastern tent caterpillars. Caterpillars are often parasitized by braconid and chalcid wasps. Tent caterpillars are also fed on by other insects such as assassin bugs and paper wasps.
Before spraying insecticides for eastern tent caterpillars, keep in mind that trees that are defoliated early in the season will typically put on new leaves. Also, insecticides are not very effective on mature larvae, so they should be used when caterpillars are an inch or less. If the tent caterpillars have been allowed to feed and complete their development, it would be pointless to spray an insecticide.
Insecticides can be used on the webs as a spot treatment. You should apply them in the early morning or evening so the caterpillars will be in the web when you spray the insecticide.
Some naturally derived products that are used to control tent caterpillars include Bacillus thuringiensis (Bt) variety kurstaki, spinosad, and insecticidal soaps. All of these products will control the smaller caterpillars. When using Bt or spinosad, spray the plant thoroughly so that the product will be eaten by the caterpillars. Insecticidal soaps must be sprayed directly on the caterpillars to kill them.
Plant derived insecticides for controlling tent caterpillars include active ingredients pyrethrum and d-limonene. There are also synthetic pesticides such as pyrethroids and carbamates that provide longer residuals than the plant derived insecticides. Some of the active ingredients include: bifenthrin, cyfluthrin, permethrin, and carbaryl. Since these are broad spectrum insecticides; it will kill the caterpillars along with the beneficial insects. Always read and follow the instructions on the product label.
Bessin, Ric. Eastern Tent Caterpillar. University of Kentucky Entomology Publication: Entfact-423. https://entomology.ca.uky.edu/files/ef423.pdf
Hahn, Jeffrey. Eastern Tent Caterpillars. University of Minnesota Extension. https://extension.umn.edu/yard-and-garden-insects/eastern-tent-caterpillars