Browntail Moth Update from the Maine Forest Service

Browntail moth caterpillars can be identified by the two distinctive orange dots at the tail end and white tufts along the sides.

This week, we observed browntail caterpillar emergence at all of our monitoring sites. It should be noted that although emergence was seen at every site, not every web has had caterpillar emergence. This is likely because of the recent rainy weather we’ve been experiencing across the state. Rainy spring weather is a great start for an epizootic outbreak of the pathogens (fungal and viral) that attack browntail caterpillars. Although it is still a bit early for the fungus and virus to have a huge impact on the caterpillars, we welcome the coming rain. Rain is also very beneficial to the health of the host trees since the state has had relatively dry spring weather the past few years. These rain events will help invigorate host trees and allow them to tolerate some of the defoliation they will experience.

At most sites, we observed that many host plants (oaks, apple, cherry, crabapple, elm, birch, poplar, shadbush, and rugosa rose) had newly emerged leaves, which make nutritious meals for the young browntail caterpillars. Even though they are small, their hairs readily break off and can cause an irritating rash to areas of exposed skin. Please plan ahead to avoid exposure to hairs and treating symptoms related to exposure.