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.

How can I get rid of caterpillars on the side of my house? +

  • Use a wet/dry vacuum with a HEPA filter filled with a few inches of soapy water.

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All Frequently Asked Questions

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Dial: 211 or 866-811-5695
Text Zip Code to 898-211
Email: info@211maine.org

News

Browntail Moth Update #5: May 19, 2023

Very late last week, after our monitoring site visits were complete, we received a report of some browntail caterpillars that had developed to the fourth instar (life stage), which we confirmed at most of our sites this week. Fourth instar and older caterpillars have white markings on the sides of each body segment and have more of the irritating hairs that cause human health impacts. This is a tipping point for this species in terms of the number of irritating hairs as well as the growing appetites of the caterpillars. Feeding damage is apparent on some branches, and over the next couple of weeks, as the caterpillars grow, they will defoliate host plants from the top down, seemingly overnight.

Image of two browntail caterpillars, one in third instar (no white stripes) and one in fourth instar (broken white stripes).
Comparison of 3rd (Top) and 4th (Bottom) instar caterpillars. Note the white tufts on each side of the body segments and the more abundant hairs.

As mentioned in previous updates, our native eastern tent caterpillar (ETC) webs can often be confused with browntail caterpillar webs. At this time of the year, ETC web development has surpassed browntail webs in size, reaching the size of a football in many areas around Maine (see photo below).

Image of a tent caterpillar nest web. Demonstrating that they are larger than browntail webs.
Native eastern tent caterpillar webs are now much larger than browntail caterpillar webs in many areas; also, note the web’s position on the host plant and appearance of the caterpillars, Unity ME.

Dealing with Wandering Browntail Moth Caterpillars

Windy weather and the fact that the caterpillars are growing larger means that caterpillars may soon be found crawling on the sides of houses, decks and around your dooryard. This means that there may be an increased chance of people coming into contact with the caterpillars, so caution should be exercised in areas of high infestations. These wandering caterpillars are also quite capable hitchhikers, and care should be taken not to spread them to other areas. Look for an upcoming update for more information on browntail hitchhikers.

Image of a browntail caterpillar crawling on the railing of a deck.
Fourth instar caterpillar crawling on the railing of a deck, Dresden, ME

If you wish to remove caterpillars from decks, buildings, driveways and other surfaces, do it in a way that will not increase your risk of exposure to their hairs (do not use leaf blowers! People get rashes this way because it stirs up the hairs). You can dislodge them from areas out of reach with a strong jet of water. To remove them more permanently, add a couple of inches of soapy water to the canister of a wet/dry vacuum, vacuum them up, and allow them to sit for a day or two, until the caterpillars have drowned. Then safely dispose of the contents (bear in mind, the toxin in the hairs is stable and may still cause irritation).

Image of browntail caterpillars huddled on their web with feeding damage further out on the branch.
Fourth instar caterpillars huddled on their web. Note the feeding damage in the upper part of this photo, Brunswick, ME.

Plans for management through insecticide treatment, and some treatments, should already be made. We recommend working with a licensed pesticide applicator for insecticide treatments. In most years, treatments should be completed before the end of May to limit the buildup of toxic caterpillar hairs and host foliage loss.

Browntail FAQ Page

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Events

2023 Browntail Moth Awareness Month Webinar

Browntail Moth Mitigation Fund

Update

The Request for Applications (RFA) for the Browntail Moth Mitigation Fund is open through May 16. The fund was established to provide support to government entities or non-profit organizations in areas with significant browntail populations to reduce impacts from browntail moth. Only applications from government entities or non-profit organizations will be considered; funding is not available for individuals. The Division of Procurement Services Grant RFP/RFA page will have updates as soon as they are available. We will also include information in these bulletins.

The Maine Forest Service has finalized rules to administer the Browntail Moth Mitigation Funds.

The Browntail Moth Mitigation Fund was established to assist government entities or nonprofit organizations in areas with significant populations. We expect the request for applications (RFA) to be available soon. Look for updates on the Division of Procurement Services Grant RFP/RFA page, this webpage, or subscribe to receive 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.

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.

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 April. 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.

Browntail caterpillar treatment: If you miss the window for web removal, caterpillars can be treated with a variety of registered insecticides labeled for the type of application (such as ornamental tree or shrub, fruit tree) and effective in controlling caterpillars. Often browntail moth will not be on the label.

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 April).

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. To understand what is happening in your neighborhood, and whether you are at risk of exposure to browntail moth, learn to recognize browntail moth then inspect the trees around you. The best time of year to do this is in the winter from mid-December through March. Browntail moth is most recognizable at this stage and management can occur or be lined up ahead of the spring season.

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.