Brown-tailed moth numbers are declining in Maine

Brown-tailed moths, whose invasive caterpillars have tiny hairs that cause rashes and add dread to Maine summers, have not had a good year here.

The state noted that the caterpillars appeared to have a “more sporadic population” across the state this year than in the past, a Maine Forest Service newsletter said Thursday.

They were recorded on more than 46,000 hectares of the state in 2023 and are damaging both forests and people.

Their more scattered populations this year are likely due to pathogens affecting the caterpillars, the state said. According to the Forest Service, wet conditions last spring and summer contributed to the spread of these pathogens, and they have continued to affect the caterpillars this year.

With the right weather conditions, they could still reappear in the coming seasons in the areas where they became extinct.

The state examines trees from the air every year to record damage to leaves caused by the caterpillars. Earlier this spring, surveys found 2,000 acres of leaves had been damaged by the caterpillars, a significant decrease from previous years. In 2022, the peak of the population boom, 250,000 hectares of damage was recorded.

The Bangor Public Works Department, which monitors collection sites for adult moths, reported in late July that they had found fewer than a dozen moths total in places where there were hundreds last year.

It was harder to see nationwide where the caterpillars had eaten through parts of the leaves later in the season because of early discoloration due to dry weather, the Forest Service said.

As the leaves fall, you can inspect your trees yourself for signs of the caterpillars, such as their winter webs. This will help you plan to eliminate them in early winter by cutting them from your trees between October and mid-April, when the caterpillars hatch.

You can also have your trees professionally injected with chemicals that will kill the caterpillars.