September 23, 2018
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Contact with toxic browntail moth cocoons can cause blistery rash, state warns

Courtesy of the Maine Forest Ser
Courtesy of the Maine Forest Ser
The invasive browntail moth caterpillar is abundant in Maine, and they can be harmful to humans. Microscopic hairs on the caterpillars can cause “a blistery, oozy rash and respiratory distress,” according to the Maine Forest Service.
By Abigail Curtis, BDN Staff

Maine officials are warning residents to be very careful before removing the cocoons of the browntail moth, a toxic, invasive species that is spreading throughout the state.

“Do this with extreme caution,” a media release issued Thursday from the Maine Department of Agriculture, Conservation and Forestry, said of cocoon removal. “Cocoons are full of the hairs that can cause a rash or worse.”

Browntail moth caterpillars have poisonous, irritating hairs that can cause a blistery rash similar to poison ivy when people come into contact with them. The hairs also can cause respiratory distress if people breathe them in.

It has been a problem in the Casco Bay and southern midcoast areas for years, and recently has expanded its footprint, according to the department. The species now is found in varying population densities over more than 6,500 square miles of Maine, the news release stated.

Courtesy of Maine Forest Service
Courtesy of Maine Forest Service
Invasive browntail moth cocoon wrapped in invasive common buckthorn leaves beneath defoliated bur oak.

The insect originally came to North America from Europe in 1897, when it was accidentally introduced to Somerville, Massachusetts. By 1913, it had spread to all of the New England states, New Brunswick and Nova Scotia. The population of the pest decreased until the 1960s, when it was only found on Cape Cod and on some Casco Bay islands, but that has changed.

Starting in the 1990s, the browntail moth has been a perennial problem along the southern Maine coast and now in other parts of the state.

The browntail moth caterpillars overwinter in webs that usually are at the top of oak trees but also in apple trees and sometimes birch. An exposure risk map based on defoliation, winter web surveys and observation shows that the browntail moth still is most prevalent around Casco Bay and the towns of Jefferson and Turner, but is on the move. Winter webs recently have been detected as far north as Old Town, as far east as Trenton, and as far southwest as the York County town of Parsonsfield.

In the spring, the larvae crawl out of the webs to feed on new leaves, according to the department, and by late June they are fully grown. That’s when the caterpillars spin rough cocoons in which they pupate, and from which they emerge as moths in July.

According to the department, browntail moth caterpillars wander and form their cocoons anywhere. Some of their favorite places to form cocoons are under the eaves of buildings or the undersides of anything, including such diverse objects as vehicles, firewood, canoes and baby strollers. They are also likely to form in the leaves of any plant.

The moth can spread through cocoons that have formed on cars, trucks, outdoor equipment and other items, and state officials ask people traveling between affected and unaffected areas in the next month to check their belongings closely for the cocoons.

If you choose to remove the cocoons, take precautions, state officials urge. Those include donning protective clothing such as long sleeve shirts, pants, socks, shoes, gloves, masks, glasses and protective coveralls. People should wet down cocoons before removing them, then scrape them and drop them in soapy water. Let them soak overnight before disposing of them, according to the media release from the department.

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