Browntail Moth - Euproctis chrysorrhoea (L.)

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News & Events

June 17, 2022

This week we observed most of the caterpillars at our monitoring sites spinning pupal cocoons in preparation for the next life stage. At least some pupation occurred at all of our monitoring sites. However, there are still some smaller caterpillars (about 25 mm in length), which are still active and have not pupated yet. In many places, particularly in the Midcoast and north of Augusta, we already see re-foliation of some affected trees and branches. This is undoubtedly helped by the precipitation we’ve had this past month

A cocoon wrapped in some leaves.
Browntail moth pupal cocoon with multiple individuals inside. Brunswick, ME.

The silky cocoons surrounding the pupae contain the last cast skin of the caterpillar and are full of toxic hairs. Many people become exposed to the hairs through encounters with the cocoons as they can pupate on buildings and vehicles/ trailers and host tree foliage. Residents should check vehicles and trailers for cocoons before moving them to prevent them from hitching a ride. People in areas with browntail moth populations should take precautions to minimize exposure to the caterpillars’ hairs.

Oaks north of Augusta displaying expected canopy defoliation.
Dead caterpillar on leaf

Information Request

The Maine Forest Service would like your help in locating diseased caterpillars. Infected caterpillars will have a puffy, swollen appearance and are covered in whitish/yellowish dust which is spores of the fungus. As caterpillars succumb to the fungus, they will hold tight to the branches they die on, which helps spread the browntail caterpillar-killing spores (see images below). Reports of ONLY DISEASED browntail caterpillars can be sent to foresthealth@maine.gov.

Examples of fungus-killed caterpillars.
Examples of fungus-killed caterpillars.

Research News

Dr. Angela Mech of UMaine and her undergraduate student Rachel Jalbert made an interesting discovery regarding browntail caterpillar feeding. During the first week of June. Dr. Mech’s research team discovered browntail moth caterpillars feeding on conifers, which has not been previously recorded in Maine to our knowledge. Spongy moth (formerly gypsy moth) feeds on conifers as the caterpillars mature, and has been observed defoliating hemlock and white pine in outbreak areas of the state this month. These two species are grouped in the same family (Erebidae), and there is now evidence that browntail can do the same, although far less commonly. Dr. Mech’s team confirmed this with photos, videos, and a lab experiment.

Browntail moth caterpillars feeding on spruce, note feeding damage in the top right. Credit: Rachel Jalbert.
Browntail moth caterpillars feeding on spruce, note feeding damage in the top right. Credit: Rachel Jalbert.

Contact 211 Maine for answers to frequently asked questions on browntail moths:

  • Dial 211 (or 207-874-2211)
  • Text your zip code to 898-211

Or visit our Browntail Moth FAQs.

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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


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.

Does killing browntail moth adults (moths) help with management? +

  • Moths found on buildings and in light traps are primarily males. Killing males is unlikely to reduce the next generation of browntail moth.
  • Using a bug-zapper or other device to kill insects attracted to lights is not recommended. It will kill insects that might help control browntail moth and other pests as well as browntail moths. It will also attract more browntail moths to the area. Females attracted to an area by lights tend to hang out in host tree foliage and are not captured in high numbers with these methods.

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All Frequently Asked Questions

Maine 211 - Get Connected. Get Answers.For More Information:
Dial: 211 or 866-811-5695
Text Zip Code to 898-211
Email: info@211maine.org


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 +


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.