Wisconsin Adds More Counties to Spongy Moth Quarantine List

By Blake Jackson

Recent trapping data from the Wisconsin Department of Agriculture, Trade and Consumer Protection (DATCP) shows that the invasive spongy moth has become firmly established in Green and Sawyer counties.

As a result, both counties have now been added to state and federal quarantine lists, joining much of eastern and central Wisconsin where the pest is already present.

In total, 56 of Wisconsin’s 72 counties are currently under spongy moth quarantine. These restrictions mainly affect industries such as plant nurseries, Christmas tree farms, logging operations, and sawmills.

Businesses in quarantined areas are required to enter compliance agreements with regulatory agencies, confirming that their plants and wood products are free of spongy moth before transporting them to non-quarantined regions.

Residents in affected counties are also urged to take precautions. Spongy moths can deposit egg masses on a wide range of outdoor surfaces, including patio furniture, campers, trailers, and firewood. Each egg mass can contain up to 1,000 eggs, making it easy to unintentionally spread the pest when moving such items.

“Even though spongy moth populations are down overall statewide, there are still areas of Wisconsin with significant populations, and all it takes is one person moving a camper, boat, or other outdoor items with a spongy moth egg mass attached, to start a new infestation” said Brian Kuhn, director of DATCP’s Plant Industry Bureau.

“This is very important if you are headed to areas in far western Wisconsin, Minnesota, or Iowa where spongy moth populations are sparse. A county can be infested without showing immediate damage, and it is important for everyone to practice diligence in order to keep this invasive pest from damaging more of our state’s plants and forests.”

Although visible tree damage may not always be immediate, the spongy moth remains a serious threat. Its caterpillars feed on more than 300 species of trees and shrubs, particularly oaks, and heavy infestations can lead to severe defoliation and long-term forest health issues.

For more information, contact Shahla Werner at (608) 957-5100 or shahla.werner@wisconsin.gov.

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