Eastern tent caterpillars can be identified by the black body with a white stripe that extends the length of the body and blue markings on the sides of the body. They have five larval instars (stages between each molt) and are one of our earliest caterpillar defoliators. Feeding on newly developed leaves can harm the trees and shrubs as it reduces their ability to phosynthesize and thus limits food production. Plants with compromised health are susceptible to further complications from pests and disease. Some plants are less likely to attract Eastern tent caterpillars due to the lower leaf nutritional quality. Prunus serotina trees grown in the shade have less nutritional value than those growing in full sun and therefore are less likely to attract Eastern tent caterpillars.
Young caterpillar instars (first through third) actively eat plant leaves during the day but remain in the nest at night and during overcast days. The final instar (fifth) caterpillar eats at night. Warmer weather promotes feeding for longer durations. Eastern tent caterpillars overwinter as an egg mass attached to branches or small twigs. Kansas has one generation of caterpillars per year.
Caterpillar nests can be removed by hand, with a rake or with a high-pressure spray of water. This destroys the caterpillar's protection and exposes them to predators such as birds. This is less effective for older caterpillar's because their bodies are covered in hairs which is not desirable for predators. Insecticides containing the bacterium, Bacillus thuringiensis subsp. Kurstaki, or spinosad, as the active ingredient can be used to eradicate young caterpillars. These insecticides must be ingested to be effective since they are stomach poisons. For older caterpillars, approximately two-inches in length, pyrethroid-cyhalothrin, or permethrin insecticides can be used. Apply insecticides during the caterpillars' active period to increase exposure. Pyrethroid-based insecticides will harm beneficials, such as honeybees, as well so avoid applying when pollinators are active. Contact your county or state extension specialist for further information about controlling and managing the Eastern tent caterpillar. Check out the Entomology Newsletter for additional images. (Cynthia Domenghini)