The Surprising Reason Maine Will See Fewer Brown Tail Moth Caterpillars in 2025

Sometimes, it feels like the brown tail moth caterpillar issue came out of nowhere.

Between Maine and New Hampshire, I have spent the majority of my life living in New England, but it was only in the last few years that I have heard about people dealing with the itchy rashes caused by the hairs from these caterpillars.

Actually, it was the summer of 2019 when I first heard and saw (on social media) people complaining about the rash these critters cause.

Where Did the Brown Tail Moth Caterpillars Come From?

The caterpillars are native to Europe and parts of Asia.  Problematic infestations of the caterpillars have been reported back as far as the 1500s.

It appears that the caterpillars were somehow introduced into New England and Canada in the 1800s.

They were first spotted in Somerville, Massachusetts, in the early 1890s.  By 1897, they had made their way to nearby Cambridge.

The caterpillars spread from there.  By the late 20-teens, much of Maine was dealing with serious infestations of the pests.

Of course, it is not the caterpillars or moths themselves that are the issue.  The problem is the hairs on the caterpillars.  The hairs, which can be carried by a breeze and remain 'toxic' for years, are what causes the itchy rash.

Why Are We Seeing a Decline in Brown Tail Moth Caterpillars in Maine?

According to the KJ, there are several reasons why we are seeing a decline.

First, the caterpillars have a natural 'boom & bust' cycle.  The recent cycle peaked in 2022.  This year it is about 10% of that peak.

Additionally, the caterpillars are susceptible to a fungus that grows best when we have a cool and moist spring, like what we have experienced this year.

The article explains that there are spots in the state where we will see brown tail moth caterpillars this year, but they are few and far between.

Have you noticed any issues with the caterpillars?