Forest Tent Caterpillars and Your Trees and Shrubs

Photo by Greg Hume

What are Forest Tent Caterpillars?

Forest tent caterpillars, a species native to North America, is the most spectacular of forest defoliators. These defoliators, although an infrequent pest, can cause considerable damage when an outbreak erupts. they feed on a variety of deciduous (leafy) trees and shrubs.

What does the damage look like?

Larvae feed initially on the opening buds, later consuming parts of or whole leaves of broad-leaved deciduous trees and shrubs. During high populations, forest tent caterpillars can completely strip trees and will then feed on the understory shrubs and other vegetation.

What is the life cycle of the forest tent caterpillar?

Adult moths emerge in early July and lay their eggs in a single gray-brown band 1.5-2.0 cm deep that encircles a small twig of the host tree and shrub. Within 3 weeks a young larvae forms within the egg, but it remains dormant until the following spring. When the leaves begin to open, the larvae emerge and begin to feed. During the early larval stage, they can be often found clustering in masses on the stem or trunk. The larvae feed over a 4-6 week period before becoming pupae. They form their cocoons between 2 leaves of a tree, on shrubbery, or on buildings where they can find a sheltered location. (In what looks like a tent, thus the name!)

Will my tree die?

Healthy trees grow back their leaves 2-3 weeks after defoliations. However, after repeated defoliation trees may be more susceptible to secondary insects and diseases.

How can I control forest tent caterpillars?

If you are seeing them in June at 1-2" long they are likely not feeding anymore, however there are several treatment options for this year and next. Book a Free Assessment and we’ll have one of our Certified Arborists® assess your trees for caterpillars or any other problems and suggest a program of treatment.

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