They’re everywhere this Spring. White silky tents in the crooks of tree branches, especially wild cherry trees. Inside the tent, hundreds of fuzzy caterpillars wriggle around, emerging in late morning to munch on the host tree and to putter on the ground. The Eastern tent caterpillar (Maladosoma americanum), or commonly tent worm, is back with a vengeance.
Your first reaction might be to grab the nearest can of insecticide and spray away, or to swat them onto the ground with a stick and stomp on them like I used to do, but please, don’t. These tent worms have been a part of our ecosystem for thousands of years and are an essential food source for local wildlife during the crucial breeding and nesting season when other sources are still scarce.
Yes, a particularly large colony of these fuzzy worms may denude your tree, but only temporarily. Tent worms only reproduce for one generation each year so the infested tree will have ample time to recover and leaf out again before summer. A pesky nuisance, but not a death sentence for the tree.
For years we gardeners thought that birds don’t care for fuzzy tent worms. Have you ever seen any birds pecking away at these sticky nests? Me either. But researchers at the Minnesota Agricultural Experiment Station have found otherwise. They documented over 60 bird species that eat tent worms, including local birds such as jays, orioles, nuthatches, and chickadees. Other species that eat tent worms (and the resultant adult moths) span the food chain, from insect predators and parasites to frogs, mice, bats, squirrels, skunks and even bears. Fun fact: researchers counted around 25,000 caterpillars in a day’s worth of a single bear’s poop. I wonder which lucky intern got that task?
Remember too that chemical pesticides used to kill tent worms also indiscriminately kill other types of worms such as those of monarch butterflies and our native swallowtails. Predators and parasites who subsequently ingest these dead worms may also die, thereby inadvertently worsening the infestation. And when it rains these chemical pesticides wash into the soil and over time can degrade water quality – an important consideration when the majority of our community here is on well water.
So leave the tent worms for the birds and the bears. Summer’s only a few months away. The trees will recover just fine.
