Wisconsin Plans Aerial Spray to Slow Spongy Moth Spread

By Blake Jackson

The Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), in collaboration with the U.S. Forest Service, will begin aerial treatments this June to combat the spread of the spongy moth (Lymantria dispar) in seven counties in western Wisconsin. This effort is part of the national Slow the Spread program.

Residents in targeted areas should be prepared for low-flying yellow planes, which may begin operations shortly after sunrise on selected mornings.

These aircraft will apply mating disruptors natural pheromones designed to interfere with the moth's reproductive cycle. The treatment does not kill the insects but prevents male moths from locating females, thus reducing future populations.

The spongy moth caterpillar can defoliate various trees and shrubs, causing plant stress and even death. Infestations can also have economic consequences, including the cost of removing dead trees and reducing property values. Additionally, their bristly shed skins may irritate human eyes, skin, and lungs.

“Spongy moth spreads easily through movement of egg masses and larvae on firewood, vehicles, and outdoor objects, especially during population outbreaks like those we’ve seen across central and eastern Wisconsin over the last couple of years,” said Michael Falk, Forest Pest Survey and Control Unit Supervisor at DATCP.

“Our 2025 treatment plan aims to prevent newly established populations from gaining a foothold in uninfested regions of western Wisconsin, which reduces future negative impact to our timber, nursery, and tourism industries.”

Treatments are scheduled for areas in Barron, Buffalo, Dunn, Grant, Lafayette, Polk, and St. Croix counties. The pheromone used is organic, biodegradable, and safe for humans, animals, and pollinators like bees.

Spraying schedules depend on moth development and weather conditions, so specific dates will be announced as they become available. Flights will continue daily as long as conditions permit.

Call the toll-free Spongy Moth Hotline at (800) 642-MOTH, emailing questions to spongymoth@wisconsin.gov for more information.

Photo Credit: gettyimages-ian-redding