MADISON -- Residents of 16 western Wisconsin counties can expect to see and hear loud, low-flying planes as early as sunrise starting in early-mid May. 

Small, yellow planes will be treating for invasive gypsy moth caterpillars. These non-native pests defoliate many kinds of trees and plants during their caterpillar stage, causing stress and potentially tree death. Treatment efforts are focused in western Wisconsin where gypsy moth populations are low or beginning to build, in an attempt to slow their spread.

The harmful effects of gypsy moths include the cost of removing dead trees and potential loss of property value. Caterpillars shed their skins several times as they feed, and these bristly skins can irritate eyes, skin, and the respiratory system 

“These aerial treatments are the most efficient and effective method to delay the impacts associated with gypsy moth outbreaks,” says Christopher Foelker, gypsy moth program manager. “Where this insect is well established in eastern North America, it has been a periodic public nuisance and damaging forestry pest.”

DATCP will be treating the following counties in 2019: Barron, Buffalo, Burnett, Crawford, Chippewa, Douglas, Dunn, Eau Claire, Iowa, Grant, Green, La Crosse, Lafayette, Pepin, Vernon, and Washburn.

Treatments are expected to begin in southern Wisconsin in mid-May and end in northern Wisconsin during July. Maps of treatment areas are available at

Spraying will begin as caterpillars hatch, and depends on favorable weather -- calm, with no precipitation and high humidity. Planes may start applying as early as 5 a.m., flying just above treetops over treatment sites, and continue until finished with the day’s plan or as long as weather conditions remain favorable. Spraying may last into the late morning or afternoon and may be done on weekends.

In mid-May to early June, the planes will spray Bacillus thuringiensis var. kurstaki (Btk), targeting gypsy moth caterpillars. Btk is a naturally-occurring soil bacteria that kills gypsy moth caterpillars feeding on canopy foliage. Btk is not toxic to people, bees, pets, or other animals. However, some people with severe allergies may wish to stay indoors during nearby treatment applications. Btk is used in certified organic food production.

In late June to early July, planes will spray an organic, biodegradable mating disruptor containing gypsy moth pheromone, targeting adult male moths. It inhibits the adult male gypsy moth’s ability to locate females.

Last Update: May 01, 2019 11:24 am CDT

Posted In


Share This Article