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April 10, 2012

MADISON -- Some Wisconsin residents will see and hear loud, low-flying planes as early as sunrise beginning in mid- to late April. Planes will be spraying for gypsy moth caterpillars, an invasive and destructive pest that feeds on the leaves of many species of trees and shrubs.

Stay updated

Gypsy moth caterpillar Gypsy moth caterpillar

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

Spraying is expected to begin in southern Wisconsin in mid- to late April and end in northern Wisconsin in July or August. People can also view maps of the specific spray areas on the website.

Spraying will be completed by two programs

The Slow the Spread Program (exit DNR), conducted by the Department of Agriculture, Trade and Consumer Protection, 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. This year's Slow the Spread treatments are planned in the following 22 counties: Barron, Bayfield, Buffalo, Burnett, Chippewa, Clark, Douglas, Dunn, Eau Claire, Grant, Green, Iowa, Jackson, La Crosse, Lafayette, Monroe, Pepin, Polk, Rusk, Sawyer, Trempealeau and Vernon. This spraying includes portions of Belmont Mound State Park and the Black River and Brule River state forests.

The Gypsy Moth Suppression Program, conducted by the Department of Natural Resources, serves mainly eastern and central Wisconsin where the gypsy moth is well established. In these counties, spraying is done 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. It has one gypsy moth spray treatment planned this year: Governor Thompson State Park in Marinette County. The campground and boat landing number 13 will be sprayed.

Know what to expect

Spraying depends on favorable weather conditionsócalm winds, no precipitation and high humidity. Planes may start spraying as early as 5 a.m. The planes fly very low and loudly over treatment sites and surrounding areas. Planes will remain in the area until the completion of the day's spray plans and as long as weather conditions remain favorable. Spraying may last into the late morning or afternoon.

Spraying could occur any day of the week, including weekends.

Most sites will be sprayed with Foray, which contains Bacillus thuringiensis var. kurstaki (Btk). Btk is a naturally-occurring soil bacteria that kills gypsy moth caterpillars when they ingest it.

Btk is not toxic to people, bees, pets or other animals. However, some people with severe allergies may wish to stay indoors during nearby spray activities or avoid areas to be sprayed on the day that spraying occurs.

The formulation of this bacterial insecticide used by the state's cooperative gypsy moth program is listed with the Organic Materials Review Institute as acceptable for use in certified organic food production.

The DNR Suppression site in Marinette County will receive one application of Btk, while some DATCP Slow the Spread sites in western Wisconsin will receive two applications of Btk, three to five days apart, weather permitting.

In areas with endangered species of butterflies and moths, a gypsy moth-specific product called 'Gypchek' will be used instead of Btk.

The Slow the Spread program also will spray a mating disruptor to additional sites in western Wisconsin between mid-June and early August. The pheromone in the mating disruptor makes it difficult for male moths to find female moths in low, isolated populations, preventing reproduction.

For more information about the programs or gypsy moths, visit the website Or, call the toll-free Gypsy Moth Line at 1-800-642-MOTH (1-800-642-6684) to hear a recording of the programs' current spray plans or talk to staff.

FOR MORE INFORMATION CONTACT: Colleen Robinson Klug, DNR, 608-266-2172 or Nkauj (pronounced 'gow') Vang, DATCP, 608-224-4591

Last Revised: Tuesday, April 10, 2012

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