Browntail Moths Love Your Lights

Maine Department of Agriculture, Conservation and Forestry <DACF@subscriptions.maine.gov> Fri, Jul 14, 2023 at 1:21 PM
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Turn off unnecessary outdoor lights at night to reduce browntail moth attraction to your property.

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Maine Forest Service

Browntail Moths Love Your Lights – July 14, 2023

Outdoor lights are highly attractive to browntail moth adults; which are active from now through the first week of August. When you leave your outdoor lights on at night, you attract these moths to your property. These moths are then congregated around a small area which makes it easier for them to successfully mate and lay eggs that will hatch a new generation of caterpillars in August. 

BTM light source

No, these aren’t white petals – these are Browntail Moth adults resting near a light source in Augusta, ME.

How can I prevent attracting browntail moth adults? 

  • Turn off unnecessary outdoor lights at night from July until the first week of August to dissuade moths from flying near your property.
  • Consider switching to yellow-spectrum lights instead of the traditional cool white colored lights as yellow bulbs are less attractive to the adults. 

If you already have browntail moth adults near you, you can put a HEPA filter into a wet/dry vacuum and fill the base of the vacuum with a few inches of soapy water. Vacuum the moths off the side of your house, porch, garage, or other surfaces. Leave them in the soapy water for a few days before disposing of the vacuum contents. 

BTM lights and winter webs

Preliminary analysis of data from Mech Lab at the University of Maine: Browntail winter webs were counted on 550 hardwood trees on the UMO campus and the distance to the nearest light source was measured. Nearly 70 percent of trees with more than 10 winter webs were 0-20 feet away from a light source, host trees (including favorite oaks and fruit trees) more than 40 feet from lights did not have more than 10 webs per tree. These data support that browntail moth adults are strongly attracted to light sources and that higher density populations can develop in trees near lights.

Preliminary research out of the Mech Lab at the University of Maine suggests that higher density populations of browntail moth develop near light sources, indicating the adult moths are attracted to and will fly to light sources to mate and lay eggs. A new generation of caterpillars emerge from the eggs and begin creating winter webs in these trees near the light sources.

These data suggest turning off outdoor lights at night may reduce the attraction of adult moths and subsequently the caterpillars that defoliate trees and cause skin irritation. 

Common misunderstandings with browntail moths: 

  • Do NOT use bug-zappers, glow sticks, lanterns, or other devices that use light to kill browntail moths. These devices will attract more browntail moths to the area with no guarantee that they will be killed. Further, these devices may kill insects that help control browntail moth adults.
  • Browntail Moth adults do not have toxic hairs like the caterpillars do. However, they may have residual caterpillar hairs on their bodies. Pupal packets (cocoons) are full of toxic hairs. When the moths wiggle out of their cocoons, they may pick up some of the caterpillar hairs left behind from their previous life stage. 

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