Friday, May 7, 2010

They're back... Eastern Tent Caterpillars

The Eastern Tent Caterpillar has begun its annual consumption of tree leaves and many people are curious about these visibly dramatic insects. Tent Caterpillars tend to prefer sourwoods, apples, and wild cherry trees however they can be found on a number of native and ornamental trees in the forest and landscape.

Tent caterpillars are commonly referred to as “bagworms” however this is misleading as the actual insects known as bagworms are very different in their damage and form. Tent caterpillars appear in the spring when the caterpillars emerge from their eggs. The caterpillars will then begin spinning their white silken webs and feeding on leaves. Tent caterpillars create the webs in the crotches of branches, rather than on the tips of branches.

The goal of most all caterpillars is to consume as many leaves as possible in order to prepare for pupation into an adult form. Tent caterpillars can defoliate young trees and if severe defoliation of larger trees occurs year after year, they will noticeably decline. The caterpillars themselves are not harmful to humans, pets, or dwellings however they can be considered a nuisance as they crawl around looking for new locations to spin their cocoons.

The best control for Eastern Tent Caterpillars is disruption of the webs as soon as they are observed. Parasitic wasps and other insects, as well as many bird species will help naturally control the caterpillars. A stick or broom handle can be used to rip into the silken web, exposing the caterpillars to a myriad of predators. NEVER attempt to burn the webs in the tree, as this creates a potentially dangerous situation that could harm both the tree and other structures or property.

Other control options are to spray the caterpillars or uneaten foliage surrounding the webs. Orthene and Sevin formulations for household use are effective treatment options, as are Dipel (Bacillus thuringiensis kurstaki), Conserve (spinosad), and Olympic Insecticidal Soap. Follow the label directions on spraying guidelines and applicable rates.

Remember that Eastern Tent Caterpillars are found throughout North America and are generally considered to be an aesthetic pest rather than a serious forest or landscape pest. Whenever possible, always choose the most effective, least toxic option for pest control.

Pesticide recommendations are included as a convenience to the reader. The use of brand names and commercial products or services written here does not imply endorsement by the NC Cooperative Extension Service nor discrimination against similar products not mentioned.

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