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August 26, 2014

MADISON -- The success of gypsy moth control efforts over the past decade may open up new opportunities for the private sector as the Wisconsin Department of Natural Resources considers phasing out its control program and encouraging communities to work with local contractors when scattered infestations appear.

Designed to reduce existing high gypsy moth populations so they don't cause heavy tree defoliation, the DNR Gypsy Moth suppression program is one of two state programs that have been very successful at keeping gypsy moth numbers in check. In recent years, DNR's suppression program has combated gypsy moth infestations throughout the eastern two-thirds of Wisconsin.

Although the DNR is considering phasing out its suppression program, the Department of Agriculture Trade and Consumer Protection will continue a separate initiative that focuses on delaying the spread or introduction of the gypsy moth in the western third of the state. This "Slow the Spread" initiative will continue to use aerial spraying methods as a way to slow down the movement of gypsy moth into new areas.

Andrea Diss-Torrance, a DNR plant pest and disease specialist, said at the peak of its efforts in 2004, the department sprayed some 50,000 acres in Eastern Wisconsin to control the gypsy moth. The invasive pest defoliates trees during its caterpillar stage and can devastate forests and urban landscapes if left unchecked.

However, easy methods to detect increasing local populations of the pest, effective biological controls such as the gypsy moth specific fungus Entomophaga maimaiga and targeted pesticides have given Wisconsin foresters and communities the upper hand. Demand for suppression spraying has decreased since 2004, and in 2014, DNR's control program treated just 29 acres in south Central Wisconsin.

As the need for the suppression spray program has decreased, forest health program staff members have turned their attention to increased demand for assistance in dealing with new invasive pests and diseases. Diss-Torrance said growing demand for assistance with the emerald ash borer makes private sector involvement all the more important in the fight against gypsy moths.

"The spread of the emerald ash borer now requires at least as much time as we used to spend on gypsy moths," Diss-Torrance said. "With the advent of private aerial applicators and more effective treatment options, gypsy moth control is not something only the state can do."

To help in the transition, DNR staff members have already prepared guidance on detecting increasing gypsy moth populations and control options for yards, communities and woodlots including how to set up an aerial spray. All of this assistance is available through Wisconsin's Cooperative Gypsy Moth website, (exit DNR).

Diss-Torrance credited state and community foresters for important advances in the suppression efforts in recent years, including detection of increasing populations of gypsy moth before they become a problem.

"By counting gypsy moth egg masses, a forester can estimate potential damage nine months before the caterpillars can cause it. This is plenty of time to set up treatment to prevent defoliation of trees in a community or woodlot," Diss-Torrance said. "Although the gypsy moth will never be eradicated from our state, collaboration among DNR, DATCP and local governments has controlled the damage this pest can do. The need for suppression of outbreaks has become more localized and is now best handled through local contracting."

Following Natural Resources Board approval, DNR will move forward to propose options for deactivating the gypsy moth suppression program, including consideration of how to handle potential future outbreaks on state-owned lands. DNR staff members intend to present a plan for public comment and feedback by early December. For more information about current control efforts, visit and search for "gypsy moth."

FOR MORE INFORMATION CONTACT: Andrea Diss-Torrance, plant pest and disease specialist, 608-264-9247,; Rebecca Gray, forest health program supervisor, 608-275-3273,; Jennifer Sereno, communications, 608-770-8084,

Last Revised: Tuesday, August 26, 2014

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