Ilex VS Eastern tent caterpillars ~ Malacosoma americanum

imageThese guys are often confused with fall webworms, and bag worms, although all three are quite different. Tent worm nests are active early in the season while webworms are active late season. Tent worms 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.

imageEastern Tent worms 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.image

Other than their webs making trees appear unsightly, tent caterpillars 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.

 

© Ilex – Midwestern Plant Girl

33 thoughts on “Ilex VS Eastern tent caterpillars ~ Malacosoma americanum

    • Here’s a horror story for you… I was weeding under my apples and backed into one of these, which ripped open and a bunch fell down my back! Yes! Loud screaming, stripping girl was heard for blocks around! Glad no one saw me strip, just the screaming. 😲😝😨

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    • Their gregarious habits are a bit like processionaries’, but they’re very different animals; rarely harm host plants or even crops, are poisonous if eaten but not venomous or even highly allergenic. Nothing to be scared of…beyond the normal human’s hard-wired aversion to being crawled on by anything that has sixteen legs.

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    • Their gregarious habits are somewhat similar to processionaries’, but they’re different animals. Not scary (unless you’re trying to start a new tree during a plague year). Though poisonous if eaten, they’re nontoxic otherwise. The fur is about as irritating as human hair of that length. The only thing you’d have to fear would be that hard-wired human aversion to being crawled on by anything with sixteen tiny feet.

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