Eastern tent caterpillar can weaken trees

By Pam Baytos

OSU Extension master gardener volunteer

This caterpillar is known as a “chewing pest” which consumes leaves and stems on a tree. The preferred hosts of this pest are cherry, crab apple and apple, but it occasionally will attack other deciduous ornamental shrubs and shade trees. When caterpillars are abundant, they frequently eat all the leaves on the tree, which weakens, but seldom kills it. The foliage on the host tree may be stripped from all the twigs within a distance of three feet from the nest. The silky tents spun by the caterpillars make landscapes unsightly and the caterpillars are annoying when searching for food or a suitable place to spin their cocoons.

The larvae emerged this year in early April, from a small, foam-like structure on pencil-sized twigs. Now they are getting larger and noticeable, with their thick, white tents in the crooks of trees.

Small larvae spin fine strands of silk wherever they crawl. As the larvae grow, so does the size of the tent. These tents serve as a protective site for larvae. The caterpillars feed for a period of six to eight weeks. The caterpillars do not feed within their webs, but congregate there during the night and during rainy weather. Fully grown larvae are about 2 inches long, generally black with a white stripe down the middle of the back. Mature caterpillars will leave the host tree to search for a suitable place to spin their pale yellowish cocoons. Within the cocoon the larva transforms into a resting stage called the pupa. The pupal stage lasts about three weeks. During late June and July the reddish-brown adult moths with two oblique, white bands on the forewing emerge from their cocoons. After mating, the female deposits eggs in a mass, each containing 150 to 350 eggs around small twigs on a host tree, where they overwinter.

Obviously, it is not safe for the homeowner to climb a ladder to prune out twigs and branches from the tree canopy. Burning the tent without removing it from the tree is not only seriously damaging to the tree, it can injure the gardener and may be prohibited. If the tent is accessible to the gardener from ground level, it can be removed by hand. Other non-chemical methods are allowing insects, toads, and birds to prey on caterpillars. Several beneficial wasps parasitize eggs, larvae or pupa of this pest.

To learn more about these pests, visit http://go.osu.edu/easterntent.