Mainers are so scared of browntail moths they’re killing other caterpillars

This story was originally published in May 2022.

Few things unite Mainers like browntail moth caterpillars. It’s difficult to find a resident or visitor to the state who does not support the eradication of the toxic hair-shedding larvae after last summer’s massive outbreak.

That development has complicated life for the Eastern tent caterpillar that’s nesting in trees this time of year.

While some people have no issues if the tent caterpillars are collateral damage in the fight against browntail nests , others view the tent caterpillars as innocent victims in the ongoing browntail control efforts. Ultimately, it comes down to a property owner’s tolerance for caterpillars on their trees.

Tent caterpillars are considered a nuisance pest in Maine. They don’t have the toxic hairs that the browntail moth caterpillars possess. But their preferred nesting sites are fruit trees, and if enough of them congregate on one tree, they can destroy it.

“Apple trees are their preferred host,” according to Jim Dill, pest management specialist with University of Maine Cooperative Extension. “Yes, they are a pest and yes, if a tree has a half dozen or so nests they will be a problem, but one nest in a tree will not do a lot of damage.”

Those nests look nothing like browntail moth caterpillar nests, which are almost impossible to spot now that the leaves have come out on trees.

Tent caterpillars build their nests where two branches meet on a tree. The easily spotted V-shaped nest is wrapped around the branches and the caterpillars venture out during the day to feed on the tree’s leaves and go back inside to sleep at night.

“As the caterpillars get larger, the nest will get larger,” Dill said. “It may be a couple of inches wide right now but give it another week or so and it will be 4 or 5 inches across.”

Browntail moths, on the other hand, prefer to build nests in oak trees, and Dill said any nest you see now is one left over from last year.

“Last fall when the larvae hatched, they fed for a little while and then wrapped themselves up with leaves into this little silken castle,” Dill said. “They are a couple of inches to 3 or 4 inches long at the end of branches.”

Any occupants of browntail moth caterpillar nests are long gone, so any nest that is visible will be empty.

That’s not stopping people from destroying them and, in some cases, taking tent caterpillar nests with them.

Amy Wescott thinks that’s a shame.

“There could be more awareness on identifying what you are killing first,” the Hollis resident said. “The cocoons are very different [and] the caterpillars obviously have different identifying features.”

Wescott fully supports the need to get rid of browntail moths and counts herself lucky there are none on her property. She wishes people would stop and think about the benefits of leaving some caterpillars alone, especially ones native to the area. She’s grown concerned about the number of people posting on social media advocating the destruction of any and all caterpillars in Maine.

“Our native [tent caterpillars] feed a lot of birds and creatures that eat insects, especially when those birds are feeding young,” she said. “Awareness and education will go a long ways on protecting our innocent natives.”

Birds do fly in and pick tent caterpillars off the sides or branches of trees, Dill said.

The type of protein provided by insects is crucial to female birds this time of year who are raising young, according to Maine Audubon.

For those who feel that tent caterpillars are doing more harm than good on their property, Dill said there is an easy method to get rid of them without damaging the tree.

He recommends getting a wooden stake long enough to reach the nest and then pound a nail into the end of it. Then wait until night when the caterpillars are all back inside and stick the nail into the nest and twist it around until the nest — and caterpillars — are all wrapped up around the end of the stake.

“Then you can put a torch to it or put it into a bucket of soapy water,” Dill said. “You don’t need to cut off the branch of the tree at all.”

As for the browntail moth caterpillars, Dill said they have no real predators, and the best chance to cut down their numbers for this summer is a fungus that kills them off. For that to happen, the area needs some rainy weather.

“A wet spring would do wonders for getting rid of browntail moths,” Dill said. “If the next three or four weeks are cold and rainy, it could really impact their numbers.”