Published on Wednesday, 30 November -0001 00:00
Silken webs in the forks or at the ends of tree limbs are common this spring. These webs, called tents, are the nests of the eastern tent caterpillar. Because they prefer to feed on the leaves of fruit trees, their nests are often found on apple, cherry, flowering crabapple, plum and chokecherry trees. They may also be found feeding on hardwood trees such as ash, birch, maple, oak, and willow.
Eastern tent caterpillars feed during the warm part of the day and return to their tent in the evening; they also stay inside the tent during rainy or cool weather. As the caterpillars grow larger, they also enlarge the nest. The caterpillars feed for about four weeks, but their feeding does not seriously damage healthy, mature trees, even if they completely defoliate a tree.
When fully grown, an eastern tent caterpillar is about two inches long, hairy, dark colored with a distinct white line down the midline and blue markings on the sides.
After they are through feeding they migrate to sheltered locations where they produce a cocoon. Adults emerge in early summer and, after mating, the females lay overwintering egg masses on the twigs of the trees. They hatch in early spring shortly after bud break, spin a tent on a branch or crotch near the egg mass and begin feeding.
Eastern tent caterpillars can be managed by physically removing the webs with a broom, rake or stick, and then crushing or burying the webs along with the caterpillars. Remove the web on a cool day or in the cool of the evening when the caterpillars are inside their tent.
It does no good to apply a chemical to the tent, so if you choose to use an insecticide, spray the foliage with a registered product such as Bacillus thuringiensis (Bt), permethrin or carbaryl. Do not spray the tree if the worms are more than an inch long because they are done feeding. If the fruit trees are in bloom, use Bacillus thuringiensis, a type of bacterial insecticide. This is a non-chemical product that will protect pollinating bees and is nontoxic to humans or other animals.