Browntail Moth - Euproctis chrysorrhoea (L.)

Knock Out Browntail Moth Logo.

On this Page:

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.

Close -

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.

Close -

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.

Close -

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.

Close -

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

News

Browntail moths are down, but not out - Remove winter webs before April

Browntail moth (BTM) aerial surveys revealed a decrease in populations in some areas of the state; however, there are still some towns that have high concentrations of winter webs. These include areas in towns surrounding Sebago Lake, communities in a line from Livermore Falls to Falmouth, and communities in Dedham.

It is not unusual to have single trees or clusters of trees with elevated populations amongst areas with low populations due to the caterpillars' hitchhiking nature. Communities that have BTM winter webs in their trees should make plans to remove and destroy the webs before April. Clipped BTM webs can be destroyed by soaking them in a bucket of soapy water overnight or by burning them in a contained fire - read our Winter Checklist for Browntail for tips on how to manage BTM in the winter.

If winter webs are not removed and destroyed before next month, the caterpillars will emerge from the winter webs and begin feeding on host trees, causing defoliation and increasing risk for their hairs to cause an irritating rash in humans. Even small numbers of webs can result in thousands of wandering caterpillars come spring (there are dozens to several hundred caterpillars in each web).

There are only a few weeks left to remove BTM winter webs before the caterpillars emerge in mid-April.

Image: Leaves that do not fall from the tree in the winter are called marcescent leaves (green arrow). BTM winter webs are leaves that are tighly bound together with white silk - an appearance that makes them stand out from single marcescent leaves (red arrow).
Image: Leaves that do not fall from the tree in the winter are called marcescent leaves (green arrow). BTM winter webs are leaves that are tighly bound together with white silk - an appearance that makes them stand out from single marcescent leaves (red arrow).

BTM winter webs are roughly 2-5 inches long and are made up of a couple leaves tied together with white silk at the tips of host tree branches. Some trees, like oak, have a tendency to hold onto their leaves in the winter instead of letting them drop in the fall season, a phenomenon known as marcescence. These marcescent leaves can sometimes be mistaken for winter webs - but winter webs have a distinct white silk attaching them to the tree while marcescent leaves do not. This is why we recommend to look for winter webs on a sunny day so that you can tell the difference!

Read the new featured article "The Ups and Downs of BTM" from Northern Woodlands:

"The Ups and Downs"

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

More Browntail Moth News Updates +

Close -

Subscribe for BTM Updates

Events

    No events currently scheduled.

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.

Close -

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.**

Close -

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 +

Close -

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.

“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

Close -

#KnockOutBrowntail Business Challenge +

Click the images below for larger shareable graphics for use on social media.

Close -

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.