Eastern Tent Caterpillar

Webs of the eastern tent caterpillar are a common sight in spring, especially where wild cherry, their favorite food, is abundant. During the day caterpillars feed on leaves; the webs protect them at night. After they strip one tree of leaves they crawl to others to continue feeding. During outbreaks tent caterpillars may attack cherry, apple, hawthorne, peach, plum, witch hazel, rose, beech, birch, willow and poplar. Defoliated trees are weakened but the damage often occurs early enough so that trees can replace their leaves.

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Nest protecting larvae

Life cycle eastern tent caterpillar, Malacosoma americanum (Lepidoptera: Lasiocampidae) - 0907031
Tent caterpillars spend the winter as dark, collar shaped egg masses about 1 inch long on branches and twigs. Each egg mass contains 150-300 eggs. Eggs hatch in spring, when tree buds begin to open. Young caterpillars construct tent-like silken masses near the runk in branch crotches. They feed for 6-8 weeks before tranforming into adults.

Adults emerge in July and live less than a week—just long enough to mate. There is a single generation each year.

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Eastern Tent moth adult

Monitoring

After autumn leaf fall, look for egg masses on susceptible trees; record locations and quantities.

In May, when buds begin to develop, look for webs in susceptible trees.

Management

Remove wild cherry trees from hedgerows and fields near susceptible ornamentals.

Remove egg masses or prune twigs containing egg masses and destroy them by crushing and then coating them with a 50-50 mix of laundry detergent and water.

Remove webs when they appear in early spring. Crush them on pavement or drop them into a 50-50 detergent/water mix. Do this in the evening when larvae have returned to the web; wear gloves to avoid skin irritation.

Biological control using of Bactillus thuringiensis (Bt) can be very effective in eastern tent caterpillar control. Make applications to foliage when the larvae are small (less than 1/2 inch).

Chemical control is usually unnecessary if all of the above methods are used. If populations still exist, judicious chemical controls may be used. Chemical controls are most effective against young larvae; web size should be no more than three inches in diameter. Applications should be made in late morning when larvae congregate near the nest surface to warm in the sun.

Anyone making pesticide applications on school property must be
licensed by the Board of Pesticides Control. See Standards for
Pesticide Applications and Public Notifications in Schools.

Printable Version [PDF]

Additional Resources:

Eastern Tent Caterpillar (GotPests.org)

Eastern Tent Caterpillar Fact Sheet (University of Maine site)

Eastern Tent Caterpillar Management (University of Wisconsin Cooperative Extension)

Photo credits:

Robert L. Anderson, Bugwood.org

Ronald S. Kelley, Bugwood.org

Lacy L. Hyche, Bugwood.org