May 13, 2010 at 9:10 a.m.
Eastern tent caterpillars cause silken webs that are found in tree crotches during May. Although their tents are unattractive, they seldom injure trees. They love to eat the leaves of fruit trees such as apple, cherry, flowering crabapple, plum, and chokecherry. They have also been known to feed on other hardwood trees, including ash, birch, maple, oak, and willow.
The caterpillars are the larval form of a moth that feed during the day and retire to their tents at night. They also stay indoors during rainy or cold weather. As caterpillars grow larger, they also enlarge their nest. Caterpillars feed for about four weeks. Their feeding does not seriously damage healthy, mature trees, even if they completely defoliate a tree. Vigorously growing trees will leaf back out several weeks after caterpillars have finished feeding. When full grown, the caterpillar is about two inches long, hairy and blue with a white line running the length of its back.
An easy way to manage eastern tent caterpillars is to remove webs with a broom or a stick and crush, burn, or bury the web along with the caterpillar. Wait until they are inside their tent before removing them. If you feel you must use an insecticide, spray the foliage with a registered product such as Bacillus thuringiensis, acephate, permethrin, or carbaryl. If they are longer than one inch long, don't treat them, because they are done feeding and it doesn't help the health of the tree. If the trees are flowering, spray Bacillus thuringiensis as this insecticide is nontoxic to bees, humans, and other animals.
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