Eastern Tent Caterpillars
Order:
Lepidoptera
Family: Lasiocampidae
Species: Malacosoma americanum (Fabricius)
The
Eastern tent caterpillar, Malacosoma
americanum, is considered to be a major defoliator of deciduous trees
in the United States east of the Rocky Mountains.
Wild cherry, apple, and crabapple are the preferred host trees,
but this pest will attack on occasion ash, birch, willow, maple, oak,
poplar, and peach.
As the name implies, the immature lepidopteran larvae, or caterpillars,
construct large tents composed of silken threads.
The presence of the caterpillars along with their ugly tents make
this pest unappealing in residential or commercial settings.
Biology and Habits
In early spring, young larvae hatch from eggs and begin feeding on unfolding leaves. While foraging on foliage, caterpillars gather at a branch fork and begin to build a web, spinning a fine strand of silk wherever they go. As they continue to consume entire leaves, except for the larger veins, the size of the tent increases, becoming more noticeable to onlookers. Typically, these gregarious caterpillars do not migrate far from the tent until they are ready to pupate.
The fully grown caterpillar is about two inches (5 cm) long. It is dark in color with a white stripe down the back and a series of oval blue spots between longitudinal yellowish lines along the sides. The body is covered with long hairs, giving the caterpillar a fuzzy appearance.
Approximately
six weeks after egghatch, the mature larvae leave the host tree and seek
a protective place to spin a cream-colored cocoon.
Adult moths emerge in about three weeks, usually in late June or
early July.
The moths are light reddish-brown in color with two whitish stripes
running obliquely across each forewing.
After mating, each female deposits a single egg collar (containing
150 to 300 individual eggs) around a twig.
Then the female covers this egg collar with a substance that hardens,
providing a black shiny appearance to the egg mass.
For nine months, the insect overwinters in the egg stage.
Control
Damage to the host tree may be minimized by pruning the twigs that exhibit the noticeable black egg masses during the fall or winter months. Unfortunately, professional services are usually sought after egg hatch when the characteristic silken tents begin to appear. In this situation, removal of webbing will be most effective near nightfall when most of the foraging caterpillars have returned to their protective tent. Insecticidal treatments to the infested twigs and fully developed leaves may be performed in the daytime hours to control the foraging pests. Several insecticides, including Bacillus thuringiensis (B.t), carbaryl, chlorpyrifos and fluvalinate are labeled for such uses. Remember, always consult labeling prior to usage.
Employ
exclusion methods to prevent the mature non-feeding caterpillar from entering
buildings when they leave the host trees and crawl across driveways and
sidewalks to seek secluded places for pupation.
(Courtesy of the National Pest Control Association.)