Forest Insect and Disease Newsletter


Getting questions about forest tent caterpillar?

Phones have been ringing off the hook with sightings of forest tent caterpillars (FTC). There hasn't been this much excitement since the last FTC outbreak at the turn of the century in the early 2000's (unless you count the great variegated cutworm scare of last week).

The place to get all your questions answered is on the forest tent caterpillar webpage.

There you will find answers to all your questions like:

  • How can I keep them off my house?
  • Are they going to kill my trees?
  • Are the caterpillars good for anything?

Read all these articles and amaze your friends and neighbors with your astute observations and knowledge. You can be the FTC go-to-guy or -gal on your block and have the phone ringing off your hook.


Eastern tent caterpillar

Forest tent capterpillar nestAlthough it is a native defoliator that occurs every spring in Minnesota, few insects can rival the attention that the eastern tent caterpillar (Malacosoma americanum) draws from concerned citizens year after year. Commonly observed on cherries, apples, and crabapples, these colorful caterpillars may also feed on other hardwoods such as ash, birch, willow, maple, oak, and aspen. Named for the conspicuous tents that these gregarious colonies of moth larvae form in branch crotches during the spring, eastern tent caterpillars can completely strip trees of their foliage in just a few weeks. Egg hatch coincides with the expansion of buds and the emergence of very young leaves. The young colony quickly forms a small silken tent in a nearby branch crotch from which they venture out to feed. Leaves are consumed almost entirely, leaving only the midrib. As they move through the crown in search of food, the growing caterpillars will spin a silken thread behind them and the tents will slowly grow in size. They complete their feeding by late spring. The two-inch-long caterpillars pupate on a vertical surface such as the tree stem or nearby house; adults emerge several weeks later and lay small clusters of eggs that encircle the twigs of suitable hosts by the end of the summer. While the loss of foliage can be unsightly and may temporarily stress a heavily infested tree, rarely does any long-term harm result. Trees will leaf out again in late spring and will have adequate time to recover before the end of the growing season. Insecticide applications are rarely necessary. The caterpillars retreat to their nest at night or during cool rainy weather, and this is a prime time to simply remove the nest and dispose of the colony. Even better: remove egg masses in the winter time to avoid the problem altogether. Birdwatchers can pull the nest apart to expose the young caterpillars to insectivores such as bluebirds... then sit back and just enjoy the show!