Browntail Moth (BTM) Frequently Asked Questions

Browntail Moth Faqs (PDF)

Biology

  • 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.
  • Caterpillars in their third larval stage begin to develop the toxic hairs, larger caterpillars have more of the toxic hairs.
  • 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.
  • Browntail moth caterpillars feed on a wide range of broadleaved trees and shrubs.
  • Preferred trees include oak, apple, crabapple, pear, birch, cherry as well as other hardwoods.
  • Adults emerge in July and are flying through August. Peak activity around lights at night is between 10 pm and 12 am.
  • There is a possibility of adult moths picking up the toxic hairs from the caterpillar stage as the moths emerge from their cocoons; however, the brown hairs on the abdomen are not the toxic hairs.
  • The caterpillars, pupal cocoons, and shed skins have the toxic hairs that can cause a skin rash.
  • The hairs on the adult moths are not toxic and do not cause a skin rash.
  • The greatest risk for exposure to the toxic caterpillar hairs is between April and July.
  • Caterpillars, shed skins, and pupal cocoons all have toxic hairs that can cause a skin rash.
  • The toxin is stable in the environment for 1-3 years and hairs can become airborne if disturbed, so one should take precautions year-round in heavily infested areas.
  • Contact the Maine Forest Service forest entomologists at (207) 287-2431.
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    Management

  • Report your detection to the Maine Forest Service if this is an area outside those where the browntail moth is widespread by going to www.surveymonkey.com/r/btmreport
    A risk map of infested areas detected through survey is available at: www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm#survey_mgmt
  • A wet/dry vacuum with a HEPA filter and filled with a few inches of soapy water.
  • Keep outdoor lights off at night during the last week of June to the first week in August
  • Egg masses are usually found on the bottom of the leaves of host trees (oak, apple, crabapple, pear, birch, cherry, and other hardwoods). Clip off affected leaves with gloved hands and soak the eggs in soapy water for two days then throw them away.
  • Learn to recognize and avoid skin contact with caterpillars. A key feature is two orange dots on the tail end.
  • Pesticides can be used to control caterpillars. The Maine Forest Service recommends contracting with a licensed pesticide applicator to control browntail moth. Products must be labeled for the site of treatment.
  • Pesticide treatments should be done before the end of May. Later treatments will not reduce human exposures to the toxic hairs.
  • A list of contractors willing to do browntail work can be found here: www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm
  • Use a wet/dry vacuum with a HEPA filter filled with a few inches of soapy water.
  • On a damp morning, use a lawnmower with a bagger to bag clippings and remove from the site. You can also hire a lawn mowing company to do this work.
  • Place a tarp or plastic under trees before treatment with pesticides. After treatment, remove the tarp/ plastic from the site, dispose of caterpillar carcasses and rinse tarp/plastic off outside.
  • Equipment that can be used includes a pair of hand snips, hand saw, and/or pole pruner, eye protection, clothing to cover skin and gloves.
  • Removing webs only requires snipping out the nest itself rather than the entire limb.
  • Collect nests and burn or soak in soapy water 3-5 days then throw them away.
  • Clipping and destroying webs in the fall and winter can reduce populations.
  • Pesticide applications can provide relief if webs are not within reach. The Maine Forest Service recommends hiring a licensed pesticide applicator for a pesticide application
  • Licensed arborists can be hired to clip webs that are not within reach or are near hazards such as powerlines.
  • A list of contractors willing to do browntail work can be found here: www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm
  • If you plan to hire a contractor, be aware that the demand for services is high. Try to line up services early.
  • Late October to mid-April.
  • When the trees and shrubs are dormant.
  • Work with a partner, especially when working from a ladder or from a lift
  • Wear protective eyewear.
  • Wear gloves, long sleeves, and pants. Trees and shrubs may have toxic hairs from caterpillar activity.
  • Individuals with known sensitivity to browntail moth hairs may want to leave web clipping to others.
  • Do not clip webs that are outside your skill set (i.e. too high or near hazards such as powerlines), hire a professional.
  • A list of contractors willing to do browntail work can be found here: www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm
  • Some libraries have sets of pole pruners for loan. You may also be able to rent pole pruners.
  • With care, a stable ladder, such as an orchard ladder or a lift can help in access to higher webs
  • Some trees are too big to practically manage through web clipping, even by professional arborists. Properly applied insecticides can work for population reduction in these trees.
  • The Maine Forest Service maintains a list of licensed arborists providing pruning services that can be found at www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm.
  • The Maine Forest Service maintains a list of licensed Arborists willing to clip nests www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm. If you already have a relationship with a licensed arborist reach out to them in September to line them up for winter web removal.
  • An Arborist for hire must be state licensed and insured.
  • For more information on hiring an arborist see: www.maine.gov/dacf/php/arborist/index.shtml
  • 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.
  • Clip and destroy any webs that are within reach during the dormant season (October through Mid-April)
  • Talk to your neighbors, they may be willing/able to help if they are already treating their trees. However, unless they are licensed pesticide applicators, they cannot treat trees on your property with pesticides.
  • Tree removal is an option to manage browntail moth, but the benefits of mature trees should be weighed against removal; removals can be followed by the planting of non-host trees.
  • Follow precautions to reduce exposure to browntail moth hairs.
  • Yes, however, consider the following:
    • Treating browntail moth in your yard will not impact the overall population. It can provide some relief in the treated areas for normal outdoor activities
    • Adult browntail moths are strong flyers and may find your treated trees from long distances, not just nearby untreated properties
    • Understand that there are many reasons people may choose not to treat browntail moth with pesticides. Having a conversation may help come up with an approach that works for the whole neighborhood.
  • If there are trees that can serve as a host for browntail on your property removal and planting a non-host tree such as a red or sugar maple is a viable option.
  • Tree removal can be successful year-round but is best performed from August to April.
  • Benefits of mature trees should be weighed against removal.
  • 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.
  • The Maine Forest Service maintains a list of licensed pesticide applicators willing to treat trees: www.maine.gov/dacf/mfs/forest_health/invasive_threats/browntail_moth_info.htm, you can also find a list of all for hire companies on the board of pesticides control website, applicators for
  • A pesticide applicator must be properly licensed and insured to treat your property.
  • Contacting a licensed pesticide applicator should be done as soon as you think you'll need one as there are a limited number of licensed applicators willing to treat for browntail moth
  • The Maine Forest Service or Board of Pesticide control can answer questions related to BTM management.
  • Maine Forest Service: (207) 287-2431
  • Board of Pesticide Control: (207) 287-2731
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    Pesticide Options

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    Health Concerns

  • A skin rash on any part of your body that was exposed. The rash tends to be red, bumpy, and itchy. It can cause discomfort for hours to weeks.
  • Respiratory issues such as breathing difficulty can occur if the browntail moth hairs are inhaled.
  • If you are having trouble breathing, swallowing, or swelling of your mouth, tongue, or throat, call 9-1-1.
  • Mild rashes can be treated at home with:
    • A cool bath with baking soda or Aveeno Oatmeal Bath
    • Hydrocortisone cream, such as Cortaid, sparingly to the itchiest areas
    • Calamine or caladryl lotion
  • If home remedies are not working, see your healthcare provider. There are medications that your healthcare provider might recommend.
  • Be careful not to apply any creams or lotions to places where young children may rub them into their eyes or mouth.
  • You can take allergy medications for mild respiratory symptoms (e.g. runny nose, sneezing).
  • If you have asthma, an inhaler may reduce symptoms.
  • Call your healthcare provider if your symptoms continue.
  • If you have difficulty breathing, swelling of the mouth, tongue or throat, call 9-1-1.
  • You cannot "catch" the rash from another person like you can a cold. The hairs need to come in contact with your skin, mouth, throat, or respiratory tract for symptoms to appear.
  • If you suspect that a fruit or vegetable is contaminated with browntail moth caterpillar hairs, you should not eat the fruit or vegetable unless it can be peeled and/or cleaned to completely remove the hairs.
  • Leafy vegetables may be more difficult to clean and may have a greater chance of retaining the caterpillar hairs, even after the washing process.
  • Ingestion of the hairs is a concern because of possible allergic reactions in the mouth, throat, and esophagus, as well as the possibility of breathing in the hairs, which could cause respiratory issues.
  • There is not enough research available on browntail moth caterpillar hair toxin to know if individuals can build up a tolerance to the toxin.
  • There is not enough research on browntail available on browntail moth caterpillar hair toxin to know if the reactions will increase in severity each time an individual is exposed.
  • You can contact the Maine Center for Disease Control and Prevention (Maine CDC) for more information at 1-800-821-5821.
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    Reducing Toxic Hair Exposure

  • The greatest risk for exposure to the toxic hairs is between April and July.
  • Caterpillars, shed skins, and cocoons all have toxic hairs.
  • The toxin is stable in the environment for one to three years and hairs can become airborne at any time.
  • It is important to take precautions year-round in heavily infested areas.
  • When working in heavily infested areas, wear proper protective equipment to reduce exposure including:
    • Long sleeves
    • Long pants
    • Goggles
    • Dust mask/respirator
    • Hat
    • Disposable coveralls
  • Avoid heavily infested areas between April and August, don't use leaf blowers or lawnmowers on dry days in these areas
  • Using pre-contact poison ivy wipes can help minimize hairs sticking into exposed skin
  • Do yardwork on wet days, which decreases the likelihood that the hairs will become airborne.
  • Make sure to use a HEPA filter on a wet/dry vacuum to decrease the likelihood that the hairs will become airborne.
  • Do not dry laundry outside in infested areas.
  • Take a cool shower after working in an infested area. This will help wash away any hairs on your body.
  • Consider using disposable coveralls for outside work. Take care in removing protective clothing.
  • You can contact the Maine Center for Disease Control and Prevention (Maine CDC) for more information at 1-800-821-5821.

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    Public policy/Economic impacts

  • Browntail moth is not a pest that can be eradicated. It has been in the United States for more than 100 years. Populations at low levels can escape notice. Browntail moth travels readily on vehicles, plants and other carriers and the adult moths are good flyers.
  • The state agencies are committed to coordinating within state government and with others outside to respond to this issue. However, the responsibility for making decisions and raising necessary resources for pest control projects is most appropriately handled at the local or individual level.
  • The Maine CDC works to provide information to health care providers and the public about the health risks from browntail moth.
  • The Maine Forest Service works with cooperators to develop tools for management and provide the technical support necessary to respond to towns, businesses and private individuals to manage this and other pest situations.
  • The Board of Pesticides Control is committed to providing the information needed to support the proper use of pesticides.
  • Currently, the state is:
    • supporting and conducting research,
    • tracking infestations,
    • supporting public nuisance declarations and
    • providing education to individuals, municipalities, businesses and others on response options.
  • A public health nuisance declaration allows a municipality to take actions to address an issue of public health concern affecting the community.
  • Where browntail moths are concerned, a declaration can allow the municipality to use public municipal funds on private lands to control for browntail moth populations.
    • More specifically, a municipality may conduct aerial spray operations to target browntail moth infestations pursuant to Maine Statute Title 22, 1444. Other options may be available to control browntail moth populations and should be discussed with Maine Forest Service.
  • A declaration can provide a municipality with more options for browntail moth treatment that may not have otherwise been available absent the declaration.
  • A declaration does not provide access to additional state funds or services. To petition for a browntail moth public health nuisance declaration, please follow the steps outlined here: www.maine.gov/dhhs/browntailmoth.
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    This information is courtesy of Maine Department of Agriculture, Conservation, and Forestry (DACF) and mirrors their browntail moth faq.