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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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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Will there be additional funding for browntail moth mitigation activities for residents and towns? +

  • Unfortunately, there are no grant opportunities through the state for browntail moth mitigation activities at this time. In 2022, a one-time funding opportunity was created and made available to towns and non-profit organizations with moderate to high levels of browntail moth to help applicants reduce the impacts of browntail through education, mechanical, and chemical control.

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All Frequently Asked Questions


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News

Browntail Awareness Month: Are you prepared?

Browntail Moth populations have decreased in 2024, however, some areas may still experience localized impacts; rashes in humans and tree defoliation. We expect areas with lower populations of browntail moth may still result in unexpected encounters with the caterpillars in May and June. Help us reduce those surprises by supporting awareness of browntail moth before they emerge!

February is Browntail Moth Awareness month and is a great time to learn how to recognize and remove winter webs from your trees - and what to do if you can't reach the webs.

Browntail moth caterpillars in a line

February Checklist

Reduce browntail impacts:

  1. Recognize browntail winter webs, which are usually at the tips of tree branches and look like palm-sized (2-5 inches long) structures covered with white silk. Focus your attention on tree species browntail strongly prefer like oak, apple, crabapple, cherry, birch, poplar, shadbush, and rose bushes.
  2. Remove webs: Use hand snips or an extendable pole pruner in areas within reach of the ground and away from hazards such as powerlines. Protect your eyes and skin during removal as toxic caterpillar hairs may still be present. After removal, destroy webs:
    • Obtain a burn permit and burn them in a contained fire, or
    • Soak them in a bucket of soapy water for a few days before disposing.
  3. Professional Assistance: When you can't reach the webs, reach out to licensed arborists or FAA-certified drone operators specializing in browntail removal.
    • Pesticide treatments may also be effective. It is not too early to find a contractor.
    • Any pesticide treatments to reduce browntail caterpillars should be completed in mid-April to mid-May to be effective.
  4. Community Support: Contribute to the relief in your community by hosting winter web surveys and clipping parties to reduce impacts from browntail caterpillar hairs. The more neighbors, businesses, and others that work together to respond to browntail, the better the results.
(Left) Browntail webs that have been removed from a tree; note that they are at the tips of branches and are palm-sized. (Right) Collected browntail webs that are ready to be destroyed by soaking with soapy water or safely burned in a contained fire.
(Left) Browntail webs that have been removed from a tree; note that they are at the tips of branches and are palm-sized. (Right) Collected browntail webs that are ready to be destroyed by soaking with soapy water or safely burned in a contained fire.
Browntail moth caterpillars in a line
Educational sticker available at Maine Forest Service booth events to raise awareness and encourage browntail winter web removal. Find us to grab your own sticker!
Educational sticker available at Maine Forest Service booth events to raise awareness and encourage browntail winter web removal. Find us to grab your own sticker!

What we're working on this winter

Browntail populations have decreased in 2024. To understand the full extent of the reduction in browntail, we are conducting a winter web survey that will wrap up in March 2025. After the data is reviewed, it will appear on our interactive browntail moth dashboard, which will give you a rough idea about what browntail is doing in your community.

In the meantime, find answers to our most commonly asked questions on browntail moth on our website.

BTM FAQs

Sign up for our Conditions Report to stay up to date on other insect and disease topics!

More Browntail Moth News Updates +

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Events

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2023 Browntail Moth Awareness Month Webinar

Browntail Moth Mitigation Fund

The application period has now closed. The Division of Procurement Services Grant RFP/RFA page will have updates as soon as they are available. Please stay tuned for more updates.

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 2023 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 +

Click the images below for larger shareable graphics perfect for use on social media or Download All Graphics

Image Description / Suggested Social Media Text

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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Knock out browntail banner logo

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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.