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2018 Browntail Moth Information

March 20th, 2019

2018 Browntail Moth Information

The Maine Forest Service has surveyed for Browntail Moth (BTM) for decades. We have been fortunate that the numbers have been relatively low in most areas for much of the past decade providing relief for people and trees. But in the last several years we have been seeing a dramatic increase in the BTM population. This letter is to give notice to towns that have significant detected populations of BTM to facilitate response by towns and/ or their residents.

Browntail moth caterpillars have hairs that cause a rash similar to poison ivy and can also cause respiratory distress in sensitive individuals. The hairs persist for years and can continue to cause problems when mowing or other activities stir them up. The caterpillars eat the leaves of oak, apple, birch and other hardwood trees from May to early July. Feeding may eventually lead to branch dieback and can contribute to tree death. 

Browntail moth adults fly in July and lay their eggs on host trees. The eggs hatch in August and tiny -1/8” - caterpillars eat by skeletonizing the underside of leaves before they make overwintering webs. In summer 2018, particularly in Sagadahoc County, there was enough damage from the young caterpillars that it could be mapped from the air (see attached map). This and other surveys indicate that populations are potentially very high in parts of some coastal towns and abundant enough to cause significant discomfort in a far broader area.

The overwintering web survey is continuing and results will be available in early spring. The survey is conducted from the roadside in areas delineated by the aerial survey or that have experienced problems in the past and expands outward to define the generally affected area. This is not meant to be exhaustive; and so people need to check their own property if they are concerned about having BTM problems.

Below is a link to the Maine Forest Service Browntail Moth website with more information including:

  • Description of the BTM and how to control it
  • What the overwintering webs look like
  • A list of Licensed Pesticide Applicators for landowners to contact this winter about potential control work in the spring
  • State Law specific to BTM control near the ocean

To  View the 2018 Browtail Moth Dectection Survey Map click here.