Seal of Dane County County of Dane
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County Executive's Office

Gypsy Moth Suppression

May 18, 2009
Darren Marsh, Dane County Parks (608) 224-3766 or Mark Guthmiller, Wisconsin Department of Natural Resources (608) 275-3223
Land & Water Resources

MADISON, May 18, 2009 – Weather dependant aerial spraying to combat the potentially defoliating effects of the gypsy moth will take place in Dane County between Wednesday, May 20 and Friday, May 22 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 third year Dane County has participated in the state suppression program; however, Madison area had similar treatments from 1998-2003 as part of the federal Slow the Spread Program. 

There are 34 treatment areas in Dane County scheduled for an aerial spray treatment this spring.  Exactly when those sites will be sprayed can only be estimated right now, according to Marsh. 

The areas include locations throughout Dane County, including (28) City of Madison, (2) City of Monona, (1) City of Middleton, (1) Town of Middleton, (1) University of Wisconsin-Arboretum and (1) Village of Shorewood Hills.

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.  “This week, we’ll start looking at the possibility of spraying on a day-to-day basis.”

“People living near those areas who want to know when the spraying will happen have two options,” 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 http://gypsymoth.wi.gov/ and clicking on Dane County on the 2009 WI Cooperative Gypsy Moth Program Treatment Areas link.  To subscribe for e-mail notification, visit the same link as the treatment maps.  Fill out the fields on that page under “subscribe to email notification list” and submit. 

Low flying planes with experienced pilots will conduct the spray treatment.  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’s 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.