Browntail Moth Information – Basics
The adult caterpillars are approximately 1.5 inches long and are dark brown with a dashed white stripe on both sides of their body. A key identifying feature is the two posterior reddish spots on the back. As for the moth, the wings and body are white except for the distinctive brown tuft hairs at the posterior tip of the abdomen.
The browntail caterpillar feeds on the foliage of hardwood trees and shrubs. This can cause reduction in growth and occasional death for the tree or shrub. The human impact of the browntail moth comes from the toxic hairs found on the caterpillars. These hairs can become airborne and stick to foliage and other surfaces. They cause a rash similar to poison ivy that can be severe. If the hairs are inhaled it can can create a burning, stinging, itching sensation in the throat and may worsen symptoms for individuals with respiratory conditions such as asthma. Cocoons full of poisonous hairs should be carefully removed from buildings and other structures.
The browntail moth reproduces once a year, going through four stages: egg, larval, pupal, and adult. In early autumn the new larvae/caterpillars, produced by that summer’s adult moths, build winter nests to “retire” during the cold weather. The 2-4” nests are usually on the extreme tips of the tree branches, formed from a single leaf wrapped tightly with the white silk they produce. If these nests are not removed while the caterpillars are dormant they will emerge the following May/June to feed on the leaves of the host tree (usually hardwood, commonly oak and apple). By late June these larvae are full-grown and will spin cocoons in which to pupate and will develop into moths that emerge in July. The female moths then lay eggs (200-400) on the underside of leaves and cover the eggs with brown hairs from their bodies. These eggs start the cycle again, hatching in late August or early September to establish the new generation of caterpillars that emerge to feed briefly as they prepare to go dormant in their winter nest.
There are currently two basic options available for the control of browntail moths in Maine: 1) pesticides, either sprayed or injected into the tree or, 2) removal and disposal of the nests in the winter when the caterpillars are dormant. There are limitations as well as advantages and disadvantages to each approach (follow links below for detail information). It should be noted that eradication of the caterpillar is unlikely with either method, but in both cases it is possible to achieve local reduction and thereby limit/reduce the impact on humans and the damage to affected trees.
Pesticide application must be performed by a licensed applicator and is not possible in all locations (e.g. waterfront). Removal of the winter nests, when they can be accessed, is a simple way of reducing the population without significant damage to the tree. The nests can be removed either by an arborist using conventional tools and equipment or through use of a drone equipped with a specialized cutter. Note that the state of Maine does not require that the drone operator be a trained arborist (see our FAQ for more info).
Additional Browntail Moth information and Resources
There are multiple sources of information about the Browntail Moth that can be found online. In our opinion the Maine Forest Service and the Maine CDC provide the best, most comprehensive information.
Other links are provided to assist you in getting help suited to your particular situation. Please contact us if you think our drone may be the optimal solution to reducing the moths on your property.