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February 11, 2025
Browntail moths have been part of Maine’s landscape for over a century, but in recent years, their numbers have surged in some areas, bringing a few headaches along with them. Their tiny hairs can cause skin irritation and, in some cases, breathing issues—not to mention the damage they do to trees. This year, towns like Hebron, Oxford, Paris, Norway, Poland, Bridgton, Naples, and Standish are seeing a lot of winter webs in the trees. The good news? Wetter weather and naturally occurring fungi have helped keep populations down in areas that were previous hotspots. In today’s blog, we’ll break down what you need to know about browntail moths—how to spot them, understand the risks, and take steps to manage them.
Browntail moth identification in Maine
Browntail moths don’t actually start as moths. It’s their caterpillar stage that causes the most trouble. Here’s a quick rundown of what they look like at each stage so you know what to watch for in Maine.
Eggs: These tiny eggs are laid in clusters of 200 to 400 and covered with brown hairs for protection. You’ll usually find them on the leaves of oak, apple, and cherry trees and some broadleaf plants and ornamental shrubs.
Caterpillars: This is the stage that causes the biggest headaches. Browntail moth caterpillars are dark brown, fuzzy, and easy to recognize thanks to the two reddish-orange spots on their back near the end of their body. They also have a white stripe running down each side.
Pupae: When browntail moths enter the pupal stage, they wrap themselves in silken webbing to undergo metamorphosis. You’ll see these cocoons on trees and plants, and in winter, you might notice tent-like webs at the tips of branches—these are overwintering caterpillars getting ready for spring. Seeing a lot of webs now could mean a more significant problem later.
Adults: Once they emerge from their cocoons, browntail moths live only long enough to mate and lay eggs. They’re easy to spot with their fuzzy white bodies and furry-looking heads, often clinging to surfaces before their short adult life ends.
If you’re spotting webs in your trees or aren’t sure whether browntail moths are a problem on your property, Pine State Pest Solutions can help. Finding them now makes it easier to tackle the issue before spring arrives.
When are browntail moths active?
Browntail moths go through four life stages—egg, caterpillar, pupa, and adult—over the course of a year. Here’s when each stage typically occurs in Maine:
- Eggs (July - August): After mating in midsummer, female browntail moths lay clusters of 200-400 eggs on the leaves of host trees, such as oak, apple, and cherry. The eggs hatch in late summer.
- Caterpillars (August - June): The tiny caterpillars start feeding once the eggs hatch in late summer. As temperatures drop, they create silken webs at the tips of branches, where they cluster together and overwinter. In early spring (April - June), they become active again, feeding heavily before entering the pupal stage. This period is the most problematic stage, as their toxic hairs can cause rashes and respiratory issues.
- Pupae (June - July): By late June, the fully grown caterpillars spin cocoons and enter the pupal stage, undergoing metamorphosis. This process lasts a few weeks.
- Adults (July - August): By mid to late July, the moths emerge, ready to mate and lay eggs. Adult browntail moths live for only a short time—just long enough to continue the cycle before dying.
If you’re noticing winter webs or caterpillars in spring, early intervention can help prevent a larger problem.
What problems do browntail moth caterpillars cause?
Browntail moth caterpillars are more than just a nuisance—they can cause itchy rashes, breathing issues, and even damage trees and shrubs. Their tiny, toxic hairs are the main culprit, sticking around long after the caterpillars are gone. Here’s what to know:
Skin irritation
The microscopic, barbed hairs of these caterpillars can cause an itchy, pink rash, often compared to poison ivy. For some, the irritation lasts a few hours, but for others, it can linger for weeks.
Breathing problems
Inhaling these hairs can lead to respiratory issues, especially for those with asthma or other sensitivities.
Tree & plant damage
When caterpillars emerge from their winter webs in spring, they feast on leaves, stripping trees and weakening them. They’re especially fond of oak, apple, and other broadleaf trees.
The tricky part? These toxic hairs don’t just disappear when the caterpillars do. They can stay in the environment for up to three years, getting stirred up by yard work like raking and mowing. That’s why early detection and management are key.
What you can do about browntail moths
Checking your property for signs of browntail moths—especially in the fall—is one of the best ways to stay ahead of the problem. Look for silky, tent-like webs on oak, apple, and ornamental trees. Fresh, bright white webbing is a sign of active overwintering caterpillars.
If you spot webs on your property, it's also a good idea to give your neighbors a heads-up. These pests don’t respect property lines, and community awareness can help keep infestations in check.
Schedule your browntail moth assessment sooner rather than later!
While browntail moth populations have declined in some areas, they remain a persistent issue in others. That’s why many homeowners are taking a proactive approach with professional assessments and spring treatments.
At Pine State Pest Solutions, our team is actively conducting browntail moth inspections in our service area, particularly in communities showing significant BTM activity. If you’re concerned about these pests on your property, now’s the time to schedule an assessment—our calendar fills up quickly!
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