Rash-causing moths are spreading due to global warming, scientists say

A forest pest that plagues Maine residents and tourists with itchy hairs appears to be spreading due to warming temperatures, a group of scientists have found.

The brown moth is a plague in America’s most forested state, where it defoliates trees and causes a rash in humans that looks like poison ivy. The caterpillar hairs, which have been an epidemic in the state for about seven years, can also cause respiratory problems.

The growth and spread of the moth is linked to increasingly warm weather, particularly in the fall, scientists recently wrote in the journal Environmental Entomology. And, sadly, climate trends suggest that years to come could be even worse, they wrote.

Warmer fall temperatures are particularly beneficial for pesky insects, as it allows them to grow larger before hibernating for the winter, said Eleanor Groden, professor emeritus of entomology at the University of Maine and lead researcher of the study.

“If they come out of those webs as warm individuals, older individuals in terms of maturity, then they’re better able to withstand that time and you get higher populations,” Groden said. “And you get defoliation that spring, and the populations wreak havoc on anyone who has them in their yard.”

The brown tail butterfly is native to Europe and neighboring countries in Asia and Africa. It was accidentally introduced to Massachusetts in the late 19th century and is now found on the coast of Maine and Cape Cod, Massachusetts. The caterpillars become active from April to June and have been identified as “an insect of concern to both forest and human health” by the Maine Department of Health and Human Services.

The moth population has fluctuated in the decades since it arrived in Maine in 1904. But the outbreak has steadily worsened in Maine in recent years, and entomologists say that last year was the worst year for brown moth infestations in state history. .

The insects have increased in numbers and territory as the Maine Forest Service said they have spread to northern and western regions of the state over the past two years.

The study found that early fall temperatures are a key determinant of population levels the following year and that climate trends “indicate a continued increase in fall temperatures” since the resurgence of the moth in the state.

It’s another example of how climate change can worsen pest problems and endanger human health, said David Wagner, a professor of ecology and evolutionary biology at the University of Connecticut who has no not participated in the study. Climate change has already exacerbated problems with pathogenic pests such as mosquitoes and ticks, he said.

“Climate change appears to be a strong driver of this system,” Wagner said. “Thus, this epidemic may continue to increase, and it may cause great cost to landowners and great nuisance to landowners.”

Maine communities have tried many strategies to try to slow the spread of the moth, including educating residents on how to safely remove their nests. The Maine legislature is considering creating a special grant fund to pay for mitigation measures.

It’s a difficult species to manage because it spreads quickly and isn’t native to the ecosystem, Groden said.

“What we are left with is how can we alleviate the localized problem in our yards and public spaces,” she said.

Teresa H. Sadler