These guys are often confused with fall webworms, and bag worms, although all three are quite different. Eastern Tent Caterpillars (ETC) nests are active early in the season while webworms are active late season. ETC like to make their tent nests in the forks of branches, while webworm nests are located at the tips of branches. Fall webworms also enclose foliage or leaves within these nests. Tent caterpillars do not. Bag worms are single worm homes made of the foliage from the tree it has decided to call home. They mostly evergreens like junipers or arborvitae. I like to remember the difference like this… A bag can hold one, but a tent can hold many.
ETC like wild cherry, other ornamental fruit trees, ash, willow and maple trees. They tend to make their tents on the eastern side of the canopy to take advantage of the early sunlight to warm them and start their digestive systems. After a about five instar, they fall from the tent, make a cocoon and after two weeks, the moth emerges. Mating occurs and the female deposits her eggs on the tree bark. Soon the eggs change into larvae, without leaving the egg and overwinter this way. In the spring, they emerge from the egg.
Other than their webs making trees appear unsightly, ETC rarely cause major problems unless their numbers become high. They are easy to control by waiting until nightfall, when they tend to go back to the tent and pruning the branch off. It can be disposed of via the garbage or campfire. If pruning is not an option, maybe these are:
- Scrape off, discard overwintering egg masses.
- Tear the protective tents out by hand before the larvae start to feed.
- Control caterpillar movement and restrict access to feeding areas with Sticky Tree Bands or Tanglefoot Pest Barrier.
- Apply Bacillus thuringiensis (Bt-k) or Monterey Garden Insect Spray (Spinosad) to the leaves to kill feeding caterpillars.
- If necessary, spot treat with plant-derived insecticides as a last resort. Spray must penetrate silken tents for effective control.
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