Gypsy moth treatment planned in Douglas County

Planes may start applying treatments as early as 5 a.m., flying just above treetops over treatment sites.

File: Gypsy moth
A gypsy moth caterpillar sits on a tree leaf. (Photo courtesy of Minnesota Department of Agriculture)

The Wisconsin Department of Agriculture, Trade and Consumer Protection plans to treat 14 western Wisconsin counties for gypsy moth starting in early to mid-May. Residents can expect to see and hear loud, low-flying planes as early as sunrise, according to a news release from DATCP.

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 tree stress and potentially tree death. In an attempt to slow their spread, treatment efforts will be focused in western Wisconsin, where gypsy moth populations are low or beginning to build.

The following counties are scheduled for spraying: Barron, Chippewa, Crawford, Douglas, Dunn, Grant, Green, Iowa, La Crosse, Lafayette, Rusk, Trempealeau, Vernon and Washburn.

“The aerial treatments the department will be conducting are the most efficient and effective method to delay the impacts associated with gypsy moth outbreaks,” Christopher Foelker, DATCP gypsy moth program manager, said in the release. “Where this insect is well-established, it has been a periodic public nuisance and damaging forestry pest.”

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 also irritate the eyes, skin and respiratory system in humans.


Spraying will begin as caterpillars hatch, and depends on favorable weather — calm, with high humidity and no precipitation, the release said. Planes may start applying treatments as early as 5 a.m., flying just above treetops over treatment sites, and continue until finished or as long as weather conditions remain favorable. Spraying may last into the late morning or early afternoon.

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, DATCP explains. Btk is used in certified organic food production.

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

Maps of treatment areas are available at .

To receive email notifications about treatment plans, sign up at . To hear a recorded message detailing plans day to day, call 800-642-6684.

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