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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