Browntail Moth - Euproctis chrysorrhoea (L.)

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Frequently Asked Questions

Partners at Maine Forest Service, Maine Board of Pesticides Control, Maine Center for Disease Control, Cooperative Extension and others have put together an extensive list of frequently asked questions. Questions cover topics from biology, to management, to policy to pets.

When will the caterpillars be active? +

  • The caterpillars are active at two times of the year. In mid-April, they emerge from their winter webs and begin feeding and growing until they reach their maximum size in June.
  • The second batch of caterpillars hatch from their eggs in August and are active until early October when they enter their winter webs to hibernate, emerging the following spring.

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How do I avoid exposure to the browntail moth toxic hairs? +

  • When working in heavily infested areas, wear proper protective equipment to reduce exposure including:
    • Long sleeves
    • Long pants
    • Goggles
    • Dust mask/respirator
    • Hat
    • Disposable coveralls
  • Avoid heavily infested areas between April and August, don't use leaf blowers or lawnmowers on dry days in these areas
  • Using pre-contact poison ivy wipes can help minimize hairs sticking into exposed skin
  • Do yardwork on wet days, which decreases the likelihood that the hairs will become airborne.
  • Make sure to use a HEPA filter on a wet/dry vacuum to decrease the likelihood that the hairs will become airborne.
  • Do not dry laundry outside in infested areas.

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What time of year should I clip overwintering webs? +

  • The Maine Forest Service recommends clipping webs between October and mid-April before caterpillars emerge from winter webs and begin feeding on new leaves.
  • This task is more easily accomplished after the leaves have fallen from the trees as the webs are more visible.

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How do I determine if I have a high browntail moth population and what should I do? +

  • Conduct a population assessment to determine how many webs are in the trees on your property. This should happen as early as possible in the dormant season beginning in October; however, it is often difficult to spot webs in oaks until December. A guide to surveying for webs is available online here www.maine.gov/dacf/mfs/forest_health/documents/browntail_moth_citizen_science_survey.pdf
  • Contractors (licensed pesticide applicators or arborists) should be lined up as soon as a decision is made to contract for help.
  • Web clipping should happen during the dormant season, generally October through Mid-April
  • Caterpillar treatments should happen in early spring, generally before the end of May.
  • The best time to manage browntail moth is when its populations are low.

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All Frequently Asked Questions


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News

Browntail Moth Update #11: August 29, 2025

In August, browntail moth caterpillars hatch from their egg masses and begin feeding on the late summer host foliage. This year, we’ve had some trouble tracking down browntail moth egg masses to monitor their development. Browntail egg masses can be difficult to spot, but they are typically found on the underside of oak, apple, cherry, elm, birch and other hardwood host leaves.

Although there are still pockets of high browntail moth populations statewide, you may need to wait until later in the fall, after winter webs tighten up, to get a good understanding of what browntail impact may be next spring.

Browntail moth egg mass on the underside of a host leaf in Old Town, ME.
Browntail moth egg mass on the underside of a host leaf in Old Town, ME.

These newly emerged browntail caterpillars are too small to eat all parts of the late summer leaves, so they graze only the outer surface, leaving behind the leaf skeleton. Over time, this process of skeletonization causes the leaf to die and turn a copper color – a clue we use to identify browntail feeding in late summer. However, the native fall webworm, slug sawflies, and other can cause similar looking symptoms in host trees.

Identification of caterpillars is not critical this time of year because late summer management for browntail moth caterpillars is not recommended. It can be difficult to find egg masses – by the time the caterpillars have eaten enough foliage to cause leaf death, it is often too late for foliage applications to be effective. Damage from browntail moth caterpillars at this time of year is generally not severe or disruptive to the tree and there is limited production of toxic hairs. The best management practices include waiting until the winter season to survey and remove browntail winter webs from your trees. If winter web removal is not feasible, winter is a good time to line up insecticide treatments for trees in high traffic areas.

As we transition from summer into the autumn season, fallen leaves may harbor toxic browntail moth hairs. See the FAQ below for tips to avoid exposure during fall clean up activities.

Webs in Late Summer: From a Friend or Foe?

Does the web:

  • Engulf entire branches, or sometimes the whole tree?
  • Have larger (>1" long), hairy, yellowish-green bodied caterpillars crawling on it?

-->Friend! You are likely looking at our native fall webworm (Hyphantria cunea) caterpillars. These caterpillars are not a forest health concern and do not cause a rash in humans, although their webs can be unsightly in trees until they break down in the winter season. Fall webworm is having a banner summer and you can see the evidence of its success enveloping hardwoods across the state. Celebrate their success and leave them be with the knowledge that, as Wagner (2005) describes in his excellent Caterpillars of Eastern North American guide, they are "parasitoid hotels."

Fall webworm caterpillars can make large webs in late summer, but they do not have toxic hairs like browntail moth. Their webs can get large, but will break down over the winter season.
Fall webworm caterpillars can make large webs in late summer, but they do not have toxic hairs like browntail moth. Their webs can get large, but will break down over the winter season.

But, if the web:

  • Is only the size of your palm,
  • Has silken pathways leading up the branch,
  • Has small pale yellow caterpillars with a black head and two dark spots near its head,

--> Foe! You are likely looking at browntail moth caterpillars. Management is not recommended in the late summer because it is not effective, however, monitor these webs and remove them in the winter season to reduce browntail moth populations on your property.

Young browntail moth caterpillars are pale yellow and have dark spots near their black head.
Young browntail moth caterpillars are pale yellow and have dark spots near their black head.

FAQ: How do I avoid exposure from browntail moth hairs when raking leaves this fall?

If you've had browntail moth caterpillars on your property in the last 3 years, you may still have hairs in your yard that can cause a rash - especially during fall cleanup when leaf blowing, raking, and mowing are frequent. These activities can stir up the toxic hairs, so here's what you can do:

  • Wear proper protective gear to reduce exposure: long sleeves, long pants, socks and closed-toed shoes. Goggles and a mask may also be helpful.
  • Preform yardwork on wet days, or early in the morning to decrease the likelihood that the hairs will become airborne.
  • Shower after being outside to rinse off any hairs that may have settled on your skin

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General Information

Adult browntail moth white with brown abdomenThe browntail moth is an insect of forest and human health concern which was accidently introduced into Somerville, Massachusetts from Europe in 1897. By 1913, the insect had spread to all of the New England states and New Brunswick and Nova Scotia. Since that time, populations of this pest slowly decreased due to natural controls until the 1960's, when browntail moth was limited to Cape Cod and a few islands off the Maine coast in Casco Bay. Browntail moth populations are again building in Maine and are found in patches along the coast and up to 60 miles inland from the western Maine border to the New Brunswick border, with the greatest concentrations in mid-coastal Maine and the capital region.

The larval stage (caterpillar) of this insect feeds on the foliage of hardwood trees and shrubs including: oak, shadbush, apple, cherry, beach plum, and rugosa rose. Larval feeding causes reduction of growth and occasional mortality of valued trees and shrubs. Learn More: How to Identify Maine’s Main Defoliating Caterpillars (YouTube) / Life Cycle of Browntail Moth (PDF)

While feeding damage may cause some concern, the primary impact on humans by browntail moth results from contact with poisonous hairs produced by the caterpillars. Microscopic, toxic hairs break off the caterpillars and can be airborne or settled on surfaces in browntail moth infested areas. Sensitive individuals who encounter the hairs may develop a skin rash similar to poison ivy and/or trouble breathing. Symptoms can last anywhere from a few hours to several weeks and can be severe in some individuals. Learn More: Maine CDC Browntail Moth Information

Management Techniques

Focus management on populations that will directly impact people, pets and livestock or pose a high risk of contributing to spread.

For Smaller Trees & Shrubs +

Browntail web removal: Webs in small trees and shrubs, safely within reach of the ground, and without hazards such as powerlines, can be removed between October and March. Browntail caterpillars emerge from their webs and begin feeding in mid-April, therefore webs removed after this time will not contain caterpillars and not be effective. Destroy webs once removed (burn, soak for an extended period in soapy water, or dispose of in trash). With permission, you can do this on properties you don’t own or manage. If there are hazards, or you need to leave the ground, this is work for a licensed arborist.

Use extreme caution if burning webs. Never burn unless the branches have been clipped off. This type of burning requires a burn permit. For more information, please visit www.maineburnpermit.com and check the daily forest fire danger report.

Browntail caterpillar treatment: Pesticide applications are most effective for browntail caterpillars when the pesticide product can take effect before late May. Treatments after that time are not recommended and are not part of an effective integrated approach to management (or IPM strategy). Since caterpillars are already wandering to new locations, targeted applications are not possible. Further, pesticide applications at this time of year are more likely to impact other living species in your trees, including pollinators and native insects, without effectively reducing the impacts from browntail. At this time, there are many shed caterpillar skins and toxic hairs that have already built up in the environment. To have more effective control of browntail, plan to target the next generation of caterpillars by scouting out new winter webs this winter to determine which trees you may want to treat next spring

Applications must be consistent with the label directions. Consider hiring a licensed pesticide applicator. In most years, treatment should be effective (caterpillars killed) before late May. Later treatments do little to reduce both hairs in the environment and damage to hosts.

If you are managing browntail moth using pesticides within 250 feet of the mean high tide mark adjacent to coastal waters and extending upriver or upstream to the first bridge, additional rules apply.

If you are unlicensed, do not use this approach on properties that are not yours or are open to the public.

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For Webs in Taller Trees +

Hire professional help to treat webs out of reach or near hazards on the property you own or manage. Line up help during fall or winter.

Licensed Professional Arborists can remove BTM webs in larger trees and shrubs (October to March).

Arborist pruning browntail moth webs.

Unmanned Aerial Vehicle (UAV) Operators with an FAA Remote Pilot License may provide services using UAVs with attachments that physically remove webs.There is no requirement that these operators have knowledge of tree care. As in working with any professional, confirm your prospective contractor is adequately insured and qualified to provide the service.

For large trees, there are very limited insecticidal products (PDF) that are readily available to and applied by unlicensed individuals and that can legally be applied to target trees and life stages of browntail moth.** In trees where the caterpillars' hairs cause a nuisance and where it is not practical to remove the webs, Licensed Pesticide Applicators may be able to use insecticides during the growing season to manage BTM.

**Acecaps are not registered for use in Maine because the label does not meet federal standards for pesticide labeling. It is therefore not legal to use Acecaps. The Maine Board of Pesticides Control has provided support to the manufacturer to explain what needs to be changed to come into compliance and encouraged the manufacturer to work with EPA to bring their label up to standards. If we become aware of a change in status, we will update this message. You can check the current registration status by entering the product name in this database.**

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Where is Browntail Moth in Maine?

Maine Forest Service conducts surveys for browntail moth from small planes and from moving trucks. These are broad-scale surveys that do not completely cover the impacted area. You can get a broad idea of where browntail moth is in Maine from our interactive map, just updated with 2025 winter web surveys. To understand what browntail moth is up to in a specific area, take a look at host plants for webs and signs of caterpillar activity.

Browntail Moth Interactive Map

Citizen Science Survey Protocol

Aerial Detection Survey Maps +

Winter Web Survey Maps +

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For Towns and Organizations

Pruning browntail moth webs.

Focus management on populations that will directly impact people, pets and livestock or pose a high risk of contributing to spread.

Hire professional help to treat webs out of reach or near hazards on the property you own or manage. Line up help during fall or winter.

Social Media Toolkit +

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Got questions about browntail moth? 211 is there to answer them.

Know your enemy and your friends. #KnockOutBTM, not silkmoths.

Image credits: DACF except promethea larva BOMONA user Zelenaks, promethea adult BOMANA user JRTindall

 

Learn how you can #KnockOutBTM and reduce the itch at www.maine.gov/dacf/knockoutbtm.

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Learn how you can  #KnockOutBTM and reduce the itch at www.maine.gov/dacf/knockoutbtm.

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Learn how to safely remove and destroy browntail moth winter webs from the Maine Department of Agriculture, Conservation and Forestry at www.maine.gov/dacf/knockoutbtm  #KnockOutBTM

To avoid encounters with the fuzzy caterpillars, remove and destroy browntail moth webs by April. Learn how from the Maine Department of Agriculture, Conservation and Forestry at www.maine.gov/dacf/knockoutbtm  #KnockOutBTM

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#KnockOutBrowntail Business Challenge +

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Research

Entomologists with the Maine Forest Service in the Department of Agriculture, Conservation and Forestry (DACF) have teamed up with the University of Maine to track the spread and investigate the causes of the outbreak and evaluate management strategies for this daunting pest.