Monday, May 23, 2011 - 11:13am


For Immediate Release

Contact: Darren Marsh, Parks Director, (608) 224-3766 or (608) 224-3730

MADISON, May 23 , 2011 - Aerial spraying to combat the potentially defoliating effects of the gypsy moth could begin in Dane County around May 24th according to Darren Marsh, Parks Director for Dane County and the county coordinator for the Wisconsin Department of Natural Resources Gypsy Moth Suppression Program. This is the fifth year Dane County has participated in the state suppression program. However, the Madison area had similar treatments from 1998-2003 as part of the federal Slow the Spread Program.

There are approximately 906 acres at 15 different sites in Dane County. There are 12 sites in the City of Madison, one in the City of Monona and two in the Town of Middleton. This is about a third of the acreage that we had last year, stated Marsh. Exactly when those 15 sites will be sprayed can only be estimated right now, according to Marsh.

Mark Guthmiller, Regional Coordinator for the Department of Natural Resources' gypsy moth program, says, "It all comes down to the weather." The caterpillars must be of a certain size and the leaves on which they feed must also be large enough so that there's a good cover to ‘catch' the spray when it comes down. Both of those factors are influenced by the weather." Then, when the caterpillars are the right size and the leaves are big enough, we have to have the right weather conditions just to get the planes in the air," Guthmiller added. "Due to the late spring we are about two weeks behind last year."

"People living near a treatment area can be notified through daily updates when treatment is planned for a given day," Guthmiller advised. "They can call our toll-free information line 1-800-642-MOTH (6684) for daily updates as we get closer to our anticipated treatment dates, or they can receive updates via an electronic e-mail list." Site specific maps of the spray blocks can be accessed by going to the gypsy moth web portal at and clicking on Dane County on the 2011 WI Cooperative Gypsy Moth Program Treatment Area link (yellow and blue Wisconsin map on right side of the page). To subscribe for e-mail notification, visit the above website and click on the DNR Gypsy Moth Spray Email Sign Up Link just under the WI maps in the gray shaded area.

Expect to hear loud low flying planes conducting the spray treatment. The planes being used this year are the yellow air tractors commonly used for aerial applications. The spraying typically begins in the early morning when weather conditions are generally most favorable, but it can happen at any time of the day if the wind is light and there is no rain in the immediate forecast. The spray treatment uses a biological insecticide with the active ingredient Btk. Btk is a naturally-occurring soil bacteria that, when eaten by gypsy moth caterpillars, causes them to stop feeding and die. Btk is generally not harmful to people, pets or other wild species. In fact, the Btk formulation to be used this year has been listed as acceptable for use in organic production by the Organic Materials Review Institute. However, people who are concerned may wish to avoid areas to be sprayed on the day that spraying occurs or stay indoors during and for 30 minutes following the spray.


  • Dane County Parks(608) 224-3766