DATCP Contact: Christopher Foelker, 608-224-4581, christopher.foelker@wisconsin.gov
DNR Contact: Jodie Ellis, 608-266-2172, jodie.ellis@wisconsin.gov

Western and central Wisconsin counties to be treated for gypsy moth May through August

MADISON — Residents of 15 western and central 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, which may defoliate many kinds of trees, causing stress and potentially tree death. The DNR and DATCP are leading the treatment efforts against the gypsy moth.

“These aerial treatments are the most efficient and effective method to reduce the risk associated with gypsy moth outbreaks,” says Christopher Foelker, DATCP 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.”

These counties will have treatment sites: Barron, Bayfield, Buffalo, Burnett, Chippewa, Crawford, Dane, Douglas, Dunn, Eau Claire, Grant, Green, Lafayette, Rusk, and Vernon.

The gypsy moth has a wide range of harmful effects on local communities. Removing dead trees can cost from several hundred to over one thousand dollars. Loss of mature trees decreases property value. During spring and summer, caterpillars shed bristly skins multiple times while growing. Airborne bristles from the cast skins may irritate people’s eyes, skin, and respiratory system, and contact with the bristles may cause a rash.

Know what to expect


Treatment applications depend on calm winds, with high humidity and no precipitation. Planes may start applying as early as 5 a.m. and continue until the completion of the day’s plans, as long as weather conditions remain favorable. The planes fly very low over treatment sites and surrounding areas. Applications may last into the late morning or afternoon and can occur any day of the week, including weekends.


  • Most sites will be treated with Bacillus thuringiensis kurstaki (Btk). Btk is a naturally-occurring soil bacteria. It is sprayed across the tree canopy and kills gypsy moth caterpillars eating the leaves.
  • 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.
  • The formulation of this bacterial insecticide is listed with the Organic Materials Review Institute as acceptable for use in certified organic food production.
  • An organic, biodegradable gypsy moth mating disruptor will be applied at additional sites in western Wisconsin mid-June to mid-August. The mating disruptor makes it difficult for male moths to find females in low, isolated populations, preventing reproduction.

Stay updated

Treatment dates and times are weather dependent. Sign up to receive e-mail notifications about treatment plans at http://gypsymoth.wi.gov. You can listen to a recorded message about our plans by calling the toll-free Gypsy Moth Information Line at 1-800-642-6684. Press menu option 1 for updates. You can also follow treatment progress on facebook.com/widatcp, and on Twitter at #WIgypsymoth.

Treatments are expected to begin in southern Wisconsin in mid-May and end in northern Wisconsin during August. View maps of all treatment areas on an interactive map: https://datcpgis.wi.gov/maps/?viewer=gm.

Two programs

  • The Slow the Spread Program – conducted by the Department of Agriculture, Trade and Consumer Protection, focuses efforts in western Wisconsin where gypsy moth populations are low or beginning to build. The objective is to slow the westward spread of gypsy moth. This year’s Slow the Spread treatments are planned in the following 14 counties: Barron, Bayfield, Buffalo, Burnett, Chippewa, Crawford, Douglas, Dunn, Eau Claire, Grant, Green, Lafayette, Rusk, and Vernon.
  • The Suppression Program – conducted by the Department of Natural Resources, serves mainly eastern and central Wisconsin where gypsy moth is well established. In these counties, treatments are applied to reduce the number of caterpillars and prevent damage from very high populations. This is a voluntary program that works with landowners and local governments. Seven Suppression Program treatments are planned this year in Dane County.
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