Last updated: March 13, 2025
Article
Browntail Moth in Acadia: 2025 Management Update
NPS Photo/Jesse Wheeler.
The browntail moth (Euproctis chrysorrhoea) is an invasive forest pest that impacts both human and forest health. The caterpillars are about 1.5 inches long, dark brown with white stripes, and covered in barbed hairs. While the caterpillars look similar to other common species, browntail moth caterpillars can be identified by their two bright red-orange spots. Exposure to the toxic hairs produced by browntail moth caterpillars can lead to skin rash and respiratory problems if inhaled. The risk of exposure is greatest between April and July.
Browntail moth populations in Maine have been at outbreak levels since 2015, and management efforts in Acadia National Park began in early 2019. There are many host trees for this species present throughout the park, including oak, birch, apple, cherry, serviceberry, and alder. Park managers remove webs in winter, when risk of exposure is lowest, prioritizing areas that are occupied by visitors and employees.
The Maine Forest Service reported peak populations levels in 2022, measured by acres of tree defoliation and winter web surveys across the state. These numbers have declined over the past two years due to management efforts and wet weather conditions that benefit browntail moth pathogens. Initial estimates from 2024 show that browntail moth populations have continued to decrease statewide. In Acadia, winter web removal efforts in 2024-2025 also reported fewer webs on both Mount Desert Island and the Schoodic Peninsula, especially at locations that previously had the highest population levels.
For more resources on browntail moth identification, health concerns, and management, visit the Maine Forest Service browntail moth information page.
Browntail moth populations in Maine have been at outbreak levels since 2015, and management efforts in Acadia National Park began in early 2019. There are many host trees for this species present throughout the park, including oak, birch, apple, cherry, serviceberry, and alder. Park managers remove webs in winter, when risk of exposure is lowest, prioritizing areas that are occupied by visitors and employees.
The Maine Forest Service reported peak populations levels in 2022, measured by acres of tree defoliation and winter web surveys across the state. These numbers have declined over the past two years due to management efforts and wet weather conditions that benefit browntail moth pathogens. Initial estimates from 2024 show that browntail moth populations have continued to decrease statewide. In Acadia, winter web removal efforts in 2024-2025 also reported fewer webs on both Mount Desert Island and the Schoodic Peninsula, especially at locations that previously had the highest population levels.
For more resources on browntail moth identification, health concerns, and management, visit the Maine Forest Service browntail moth information page.