Every other Friday, the Outside/In team here at NHPR answers listener questions about the natural world.
Today's question comes from Sheila, who wrote the team on their listener Facebook group: “Is there evidence of browntail moth caterpillar activity in New Hampshire?"
Producer Justine Paradis has the answer.
This transcript has been lightly edited for clarity.
Justine Paradis: If you’ve never heard of a browntail moth, consider yourself lucky. A writer for the Cape Cod Times once described them as “poison ivy with wings.”
Angela Mech: They're horrible… it is one of the the absolute worst insects to have to work with.
Justine Paradis: Angela Mech would know. As a forest entomologist with the University of Maine, she helps manage the state’s browntail moth population. Browntail moths are white, with a brown abdomen. That’s where they get their name. But the issue is their caterpillars. They have tiny, barbed hairs, which they shed when they molt.
Angela Mech: And they have a toxin within the hair that causes a poison-ivy-like rash.
Justine Paradis: The biggest danger is when the caterpillars are active, from April to June. But their hairs can persist in leaf piles for years. And the kicker? You can’t see them.
Angela Mech: They are extremely microscopic. The length of one of the hairs is almost the width of a human hair, so very, very small. It's small enough to inhale, so they can cause respiratory issues in sensitive people. And, as I learned the hard way, they're small enough to get stuck behind your contact and tear your cornea.
Justine Paradis: Browntail moths have long been a scourge in Europe, but were inadvertently introduced to New England in the late 1800s. And people were not happy. They burned the nests, sprayed them with pesticides, even paid kids five cents for every 100 nests they collected (seriously). It pretty much worked. As of the 21st century, the range of browntail moths had been reduced to small pockets at the tip of Cape Cod and on the coast of Maine. But it would be unwise to let our guard down. Every 10 or 15 years or so, their population surges again.
Kyle Lombard: We've been doing a winter survey for browntail moth for 30 years, and we've always been amazed that it has not come back to New Hampshire from that site on the coast of Maine.
Justine Paradis: Kyle Lombard is a forest entomologist with the New Hampshire Division of Forests and Lands. In the summer of 2024, for the first time in 75 years, browntail moths crossed over the state line. Technically. They blew over from Appledore Island in Maine to Star Island in New Hampshire.
Kyle Lombard: The count is zero on the mainland. But Star Island still has a few. . . . We did do a control project out there this past spring where we went out and we clipped as many of the nests as we could and destroyed them. But we didn't get them all.
Justine Paradis: Kyle and his team are monitoring other high risk areas along the coast, like Odiorne State Park in Portsmouth. Which they do every winter: It’s a good time to find nests and remove them.
Kyle Lombard: Now, the good news is that the population in Maine this summer completely crashed . . . just a massive die off. It receded all the way back to that little spot along the coast where they just can't get rid of it.
Justine Paradis: We owe thanks for today’s decline at least in part to those who suffered from browntail moth rashes 100 years ago. That’s when entomologists identified a fungus which infects the moths.
Angela Mech: They artificially infested healthy caterpillars with the fungus and then they would go plant those sick caterpillars in healthy populations. They did that to 100,000 sick caterpillars, spread them out across the state of Maine.
Justine Paradis: Today, Angela and other researchers are exploring new ways to address browntail moth outbreaks — like using their pheromones to confuse the moths during mating season, and prevent them from reproducing. But funnily enough, as the population crashes, they’re racing against the clock.
Angela Mech: It’s a very short window. Once the outbreak ends, there isn't going to be enough browntail to really research for another 10 to 15 years. So, we're trying to cram in as many research projects as we can while we have them.
If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to outsidein@nhpr.org. You can also leave a message on our hotline, 1-844-GO-OTTER.
