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Browntail Moth Caterpillar in the Area in Record Numbers

Browntail Moth Caterpillar Treatments to Begin in Yarmouth

APRIL 26, 2018 - The Browntail Moth has settled in Yarmouth in record numbers this year. This pest is known for its toxic hairs, which can cause highly-irritating rashes similar to Poison Ivy and respiratory issues, and for its ability to defoliate trees and shrubs.


In an effort to protect the Town’s residents and its green space in a low-impact, environmentally-friendly manner, while also preserving the health of the trees and shrubs, the Town will be treating select Town-owned trees on public properties around Town beginning this week. Town employees and volunteers will be selectively clipping out nests in trees that are reachable by ladder and trucks. To treat the larger trees, Hughes Inc. Arbor & Land Management has been contracted for assistance. 


Trees in these locations will have the clipping done: Yarmouth High School, Yarmouth Community Garden, Yarmouth Community House, and Camp SOCI. Other locations may be identified as the process get underway.


Certain larger trees with branches that are the most difficult to reach, will be treated with an Acephate, an organophosphate insecticide. The substance is injected into the root crown, the soil near the tree’s trunk, soaked up by the roots and carried up the trunk and into the branches. It takes approximately one week for the substance to reach the highest branches, and it stays in the tree’s system for approximately one month. When the Brown Tail Moth caterpillars feed on the foliage of a treated tree, the caterpillars die.

Applied this way, the acephate does not pose a health risk to residents. The leaves themselves are only toxic to humans if they are consumed, or eaten.

Plants absorb acephate quickly from the soil into their roots or through their leaves and move it to other parts of the plant. Acephate is not being sprayed. And the substance does not tend to off-gas from soil or water.


More information about acephate can be found from the National Pesticide Information Center 


Bees are not impacted by the treatment, as the trees being injected are wind pollinated (not flower pollinated).


Acephate treatments are planned for trees in the area of Merrill Memorial Library and Yarmouth High School. Other locations may be identified as the treatments get underway.


Please observe posted signs requesting that the public stay away from certain areas for 24 hours after treatment— as required by the State of Maine. Treatment will begin as soon as the weather warms up, and there are leaves and buds on the trees. Questions can be addressed to ISA Board Certified Master Arborist Mike Hughes at (207) 232-4158 or emailed to


If you would like to volunteer in an effort to protect our trees from Browntail Moth, please contact Yarmouth Community Services at (207) 846-2406.



Browntail Moth caterpillars proliferate throughout Maine. The insect feeds on the leaves of many common hardwood trees and shrubs in Town.


It has tiny barbed hairs that can cause a skin rash and respiratory difficulties, which can last anywhere from a few hours to several weeks. The tiny hairs break off the caterpillars and are everywhere in infested areas; on trees, lawns, gardens, decks, picnic tables, and in the air. The hairs can remain toxic for up to three years. Wind or activities like mowing or leaf blowing can stir up the hairs and cause a reaction for months, even after the caterpillars become moths.


In spring and as soon as the earliest leaf buds open, Browntail Moth caterpillars feed on the leaves of many hardwood trees and shrubs including Oak, apple, crabapple, cherry, hawthorn, shadbush, serviceberry, and rugosa rose. Infestations can cause reduced growth and branch dieback. After a couple of years at high population levels, Browntail Moth caterpillars can cause the trees and shrubs to die.

The caterpillars then form filmy cocoons between leaves on trees, under eaves, picnic tables, and decks. Adult moths emerge from their cocoons in late July and fly to the tops of trees to remain over the winter months. In the next spring, the process begins again.




The Town of Yarmouth does not spray insecticides on private or public lands for any insects— including Ticks, Mosquitos, or Browntail Moth Caterpillars. So residents and visitors should take steps to protect themselves. Options include:


● Learn to identify the Browntail Moth caterpillar: it is dark brown with a broken white stripe on each side and two conspicuous red spots on the back. It typically grows to 1.5 inches in length. In July and August, the Browntail Moth has snow-white wings and a tuft of dark brown hair on the tip of the abdomen.

● Wear long sleeves, pants, hats, and gloves in affected areas.

● Wash clothes and body after leaving infected areas.

● If you are at risk of respiratory complications, please make additional considerations.

● Avoid leaf piles and areas that have not been raked or blown.

● Contact your physician if you have contracted a severe rash.


For more information:


BTM Brochure, by the Maine Dept of Agriculture, Conservation & Forestry

BTM History in Maine and Current Situation, by the Maine Dept of Agriculture, Conservation & Forestry

BTM Lifecycle, by the Dept of Agriculture, Conservation & Forestry

BTM Handling Precautions, by the Dept of Agriculture, Conservation & Forestry

Maine Forest Service: (207) 287-2431

Maine Board of Pesticides Control: (207) 287-2731

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