MADISON, Wis. – The Wisconsin Department of Agriculture, Commerce, and Consumer Protection (DATCP) plans to treat 17 western Wisconsin counties for gypsy moth, formerly known as gypsy moth, from mid-May through the end of May. Residents can expect to see and hear loud, low-flying aircraft as soon as the sun rises.

Small yellow planes will deal with the invasive caterpillars of the spongy moths. These non-native pests defoliate many types of trees and plants during their caterpillar stage, causing stress and potentially tree death. In order to slow their spread, control efforts will be focused in western Wisconsin, where gypsy moth populations are low or beginning to build.

“DATCP will perform aerial treatments, which are the most effective and efficient method of delaying the impacts associated with spongy moth outbreaks,” says Christopher Foelker, DATCP Spongy Moth Program Manager. “Where this insect is established, it has been a periodic public nuisance and damaging forest pest.”

Harmful effects of gypsy moths include the cost of dead tree removal and potential loss of property value. Caterpillars shed their skin several times while feeding, and these spiky skins can irritate the eyes, skin, and respiratory system in humans.

The following counties should receive aerial treatments: Barron, Bayfield, Buffalo, Burnett, Chippewa, Crawford, Dunn, Eau Claire, Grant, La Crosse, Lafayette, Pépin, Rusk, Sawyer, Trempealeau, Vernon and Washburn.

Treatments should begin in southern Wisconsin in early to mid-May and end in northern Wisconsin in mid-July. Maps of treatment areas are available at https://smaerialspray.wi.gov. Spraying will begin soon after the caterpillars hatch and will depend on favorable weather – calm, no precipitation and high humidity. Planes can begin applying treatments as early as 5 a.m., flying just above the treetops above treatment sites, and continue until the end or as long as weather conditions remain favorable. Spraying can last until late morning or early afternoon.

From mid-May to early June, planes will spray Bacillus thuringiensis var. kurstaki (Btk), targeting moth moth caterpillars. Btk is a naturally occurring soil bacterium that kills moth moth caterpillars feeding on canopy foliage. Btk is not toxic to people, bees, pets or other animals. Some severe allergy sufferers may wish to remain indoors during near treatment applications. Btk is used in the production of certified organic foods.

From late June to mid-July, planes will spray an organic, biodegradable mating disruptor containing a sponge moth pheromone, targeting adult male moths which inhibit the adult male moth’s ability to locate females.

To receive up-to-date information on treatment plans: