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Maine Forest Service

Browntail Moth - Euproctis chrysorrhoea (L.)

Browntail Moth News

Events

No events currently scheduled.

Recorded Browntail Moth Webinars on Collaborator Sites

Belfast Area Partners, Live presentation February 1, 2022
Belfast Free Public Library and Partners hosted Forest Entomologist Tom Schmeelk for a webinar on BTM and Emerald Ash Borer, two invasive insects of significant concern.
Hancock County Area Partners, February 10, 2022
Blue Hill Heritage Trust, Island Heritage Trust, Hancock County Soil and Water Conservation District, Great Pond Mountain Conservation Trust, and Frenchman Bay Conservancy hosted a conversation about BTM in the region with State Entomologist and Director of MFS Forest Health and Monitoring Allison Kanoti.

New Resources

Subscribe to the new Browntail Moth Update Bulletin
Overview of Browntail Moth Management for Towns and other Organizations
Updated FAQ’s (November 2021)
An interactive map with past survey data was made available in December 2021
Browntail Moth Videos

Browntail Moth Update

May 13, 2022

As noted last week, browntail caterpillars have begun producing silk and have expanded the winter webs. There is a native look-alike, called eastern tent caterpillar, that can be confused for browntail moth webs at this stage in development. Two key differences between the webs these species make are size and position on the tree. The silken nests of native eastern tent caterpillars start small but can grow quite large, reaching around the size of a football and are attached to the tree where the branches meet the trunk or come together. Additionally eastern tent caterpillars lack the two characteristic orange spots on the tail end of the caterpillar.

Browntail winter webs are the size of your palm or smaller, are constructed in late summer and early fall on the tips of the branches and are comprised of silk that also incorporates the leaves on the branch tips. As the caterpillars become active in the spring, they travel in and out of the web, and the web can become surrounded in gauzy silk similar in texture to that made by eastern tent caterpillar. Browntail moth caterpillars are dark brown and have two orange spots towards the rear of their bodies. As the caterpillars molt, they develop white stripes due to white tufts of hair on each segment.

The photo below shows an eastern tent caterpillar nest (upper) next to a browntail moth winter web (lower) (note, the eastern tent caterpillar nest is less dense and will continue to enlarge as it develops through the spring and summer).

Image: Browntail moth winter web next to eastern tent caterpillar web. MFS.

Earlier this month, the Governor signed LD1929, An Act to Provide Assistance to Areas Severely Infested with Browntail Moth, into law. The law, which will be in effect later this summer, directs the Department to create a program, in part through rule-making, to distribute $150,000 to government entities, such as cities or towns, or nonprofits to mitigate browntail moth. We will work to develop that program in the coming months, with the goal of having procedures in place by the end of 2022 so that funds can be distributed in early 2023. It is our hope that these funds will help more organizations engage in efforts to reduce the impacts from browntail moth.

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 FAQs here.

Frequently Asked Questions

What do we know about 2022 browntail populations? +

Generally speaking, we expect conditions to be as bad or worse than last year in terms of potential encounters with browntail moth and their hairs. Browntail moth populations in Maine have been in an outbreak phase since 2015, and populations continued to increase in 2021, with almost 200,000 acres of damage mapped in aerial surveys. Also, the second consecutive dry spring in 2021 limited disease in the caterpillar stage, allowing a bumper crop of moths to disperse in July 2021. We will know more about the 2022 outlook our winter web surveys.

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What are areas of Maine that are most at risk for 2022? +

Most areas of Maine, especially along the coast and inland, that have significant host tree populations are at risk. In 2021 overwintering browntail moth webs were found in every county in Maine except York. The highest populations in 2021 were found in Androscoggin, Cumberland, Kennebec, Knox, Lincoln, Sagadahoc, and Waldo Counties, with some pockets of high populations in adjacent counties. Aerial surveys revealed intensification in many areas, and first damage mapped in coastal Hancock County as well as Oxford County.

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What are the most precise ways for people to know the browntail moth situation in their area? +

Consulting our interactive survey map will give people a general idea of what the population looks like in their area. However, there is no substitute for inspecting the host trees and shrubs around places they frequent.

Late-fall through early spring: on sunny days, examine hosts for winter webs on the tips of host branches
Spring-early summer: look for the distinctive caterpillars. The white stripes characteristic of older larvae usually develop in late May. The two orange dots towards the rear are present throughout this stage.
Early summer through leaf fall, watch for and avoid cocoons and their remnants.
Late-summer watch for distinctive feeding and developing silk created by young caterpillars before overwintering
See photos below under Life Stages.

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Since toxic hairs haven’t been produced since the end of June in 2021, do I still need to be concerned about exposure? +

In areas with low browntail moth populations and individuals who are not highly sensitive to the toxins in the browntail caterpillar hairs, the risk of a reaction is reduced. This is in part because the risk of encounters with the hairs is reduced with ample rainfall after spring-feeding caterpillar activity has stopped. Consistent rain has been seen over much of the infested areas from July and into September; this will help incorporate hairs into the soil and reduce their chance of becoming airborne in drier conditions. However, sensitive individuals and people in areas with moderate to high populations in spring 2021 or prior should continue to use caution in conducting work that might stir up the hairs or otherwise lead to encounters with them. Activities such as sweeping, raking, mowing, using leaf blowers, gardening, handling firewood or other material where hairs may have settled or caterpillars may have pupated are examples of conditions that may lead to encounters with the hairs long after the caterpillars are gone.

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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

More Frequently Asked Questions - for more information

Close up of overwintering webs of browntail moth in northern red oak.
Close up of overwintering webs of browntail moth in ornamental crabapple
Caterpillar of browntail moth
Communal cocoon of browntail moth in an ornamental crabapple
Communal cocoons of browntail moth
Adult browntail moths
Browntail moth eggs and adult
Late-summer browntail moth larvae and webs
Browntail moth overwintering webs

General Information

The 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 capitol 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.

Identifying Maine’s Main Defoliating Caterpillars - YouTube

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.

Photos of Browntail Moth Life Stages +

Close up of overwintering webs of browntail moth in northern red oak.
Close up of overwintering webs of browntail moth in ornamental crabapple
Caterpillar of browntail moth
Communal cocoon of browntail moth in an ornamental crabapple
Communal cocoons of browntail moth
Adult browntail moths
Browntail moth eggs and adult
Late-summer browntail moth larvae and webs
Late-summer feeding by browntail moth and young caterpillars
Browntail moth overwintering webs

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Maine CDC Browntail Moth factsheet (PDF | .98 MB)
Got the Itch? Browntail Moth on Maine School Grounds: How to Recognize, Treat and Manage it (Maine Department of Agriculture, Conservation and Forestry. Aired 11/17/16).
Browntail Moth Brochure (PDF | 1.7 MB)
Identifying Browntail Moth Winter Nests
Browntail Moth in Maine History and Current Situation 2018 (PDF | 2.4 MB)
Browntail Moth Life Cycle (PDF | .3 MB)
Maine CDC Browntail Moth Information

Management Resources

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

Management overview for towns and other organizations (‘Municipal Battle Book’)

Do-it-yourself management techniques

These approaches may be used on smaller trees and shrubs infested with browntail moth.

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.

How to Remove Browntail Caterpillar Nests Video

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.

Removing Browntail Caterpillar Nests from Jeff Fischer on Vimeo.
2021 Browntail Moth Winter Web Moth Survey (PDF | 640 KB)

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.

Management techniques 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).

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 | 146 KB) 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.**

Managing Browntail Moth in Tall Trees in Maine (PDF | 146 KB)

Survey Resources

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 Dashboard interactive map

Citizen Science Survey Protocol

Aerial Detection Survey Maps

Winter Web Survey Maps

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. Read the report on Browntail Moth Research at the University of Maine.

Karla Boyd, Francis Drummond,Charlene Donahue, and Eleanor Groden; 2021: Factors Influencing the Population Fluctuations of Euproctis chrysorrhoea (Lepidoptera: Erebidae) in Maine (PDF)
Karla Boyd’s 2020 thesis: "The Relative Abundance and Diversity of Parasitoids of the Browntail Moth (Euproctis chrysorrhoea L.) and Factors that Influence Their Population Dynamics"

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. “browntail” in brown font
	Learn how you can #KnockOutBTM and reduce the itch at www.maine.gov/dacf/knockoutbtm. “browntail” in white font
	Knock out browntail banner logo “browntail” in brown font
	Knock out browntail banner logo “browntail” in white font
	Knock out browntail stacked logo without URL “browntail” in brown font
	Facebook-ready image. 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