Gypsy Moth Aerial Spraying to Resume Early Next Week

June 21, 2016

Contact:  Nolan Stracke, Public Information Officer,, 608-224-4591
Bill Cosh, Communications Director, 608-224-5020,

MADISON -- Residents of 14 western Wisconsin counties can expect to hear and see low-flying planes in the early morning, depending on weather conditions, starting next week. Single seat, yellow planes will be applying mating disruptor flakes specifically targeting gypsy moths. These invasive pests defoliate trees during their caterpillar stage, causing stress and potentially tree death. 

Through late June and much of July, yellow spray planes contracted by the U.S. Forest Service in a joint project with the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP), will be applying  pheromone flakes, or mating disruptor, to 28 sites in 14 counties in the western third of the state. One site in Dunn County totaling about 44,000 acres will be treated with an alternative liquid-organic mating disruptor in mid-July. 

“Female gypsy moths don’t fly. They give off a pheromone, or a chemical scent, which attracts male gypsy moths,” explained Nolan Stracke, public information officer for DATCP’s gypsy moth program. “The flakes that we apply to the tree leaves emit the same scent. This confuses the males and makes it very difficult for them to find a mate. Next spring, there should be far fewer gypsy moth caterpillars in these areas.” 

The gypsy moth has a wide range of negative effects on local communities. The cost of removing dead trees around a house can range from several hundred to over one thousand dollars and the loss of mature trees will decrease property values. During the spring and summer, caterpillars shed bristly skin as they grow. Bristles from the cast skins can become airborne and irritate eyes, skin and the respiratory system. People may develop a rash if they come in contact with the bristles. 

About the Spray Treatments 

The flakes are extremely thin, tiny green pieces that are about 1/8 by 1/16 inches. The flakes are applied to the tree leaves at a low rate so they are not easily detected. Past research shows the flakes can reduce gypsy moth populations by nearly 90 percent from one year to the next. 

“We mix the flakes with a sticking agent that is similar to white school glue so the flakes adhere to the tree leaves. We use airplanes to apply the flakes at a rate of 1-2 flakes per square foot of tree canopy,” Stracke said. “The flakes don’t harm the gypsy moth in any way; they make it more difficult, if not impossible, for a male to find a female gypsy moth.” 

The flakes are not harmful to humans, animals, birds or other insects. According to the Environmental Protection Agency, there is no health risk to humans nor have any adverse effects been reported during the nearly two decades that these pheromones have been used. 

Stay Updated 

Spray dates and times are weather dependent. People can sign up to receive email notifications about spray plans at They can listen to a recorded message about spray plans by calling the toll-free Gypsy Moth Information Line at 1-800-642-6684. Press menu option 1 for updates. 

Spraying will resume in late June and end in northern Wisconsin in late July. Maps of the specific spray areas are available online. 

Spraying will be completed by the Slow the Spread Program -- conducted by the Department of Agriculture, Trade and Consumer Protection. It focuses its efforts in western Wisconsin where gypsy moth populations are low or just starting to build for the first time. The objective is to slow the westward spread of gypsy moth. The Slow the Spread treatments are planned in the following 14 counties over the course of four weeks: Barron, Buffalo, Chippewa, Crawford, Douglas, Dunn, Eau Claire, Grant, Pepin, Rusk, Saint Croix, Sawyer, Trempealeau and Vernon.