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MDARD expands hemlock woolly adelgid quarantine to combat the spread of this invasive species

LANSING – The Michigan Department of Agriculture and Rural Development (MDARD) revised the State of Michigan’s interior hemlock woolly adelgid quarantine. The new quarantine is effective on August 1, 2023. 

The updated quarantine now includes Benzie and Manistee counties as well as a portion of Washtenaw County in and around the Nichols Arboretum after the pest was identified in these areas. The previous interior hemlock woolly adelgid quarantine regulated movement of hemlock in Allegan, Mason, Muskegon, Oceana, and Ottawa counties.

The quarantine regulates the movement of hemlock and tiger-tail spruce trees, forest products and nursery stock, with some exceptions, from the quarantine areas to other locations within the state. 

“Our goal is to protect the 170 million hemlock trees that live in Michigan’s forests,” said Mike Philip, Director of MDARD’s Pesticide and Plant Pest Management Division. “According to the U.S. Department of Agriculture Forest Service, hemlock trees have a strong impact on streamside habitat conditions and stream health. Loss of hemlock could result in a rise in water temperatures in streams and an increase in soil erosion, something Michiganders certainly don’t need to further experience." 

Trees infested with hemlock woolly adelgid should be reported by one of the following means:

“If left unchecked, hemlock woolly adelgid could spread throughout Michigan’s hemlock trees, causing significant losses and affecting the timber and lumber industries, nursery and landscaping industries, the Christmas tree industry, and the tourist industry,” added Philip. “Hopefully, by expanding quarantine area, we can keep the pest from moving to new areas in the state and slow the spread within the currently infested areas.” 

Be prepared to report the location of infested trees and, whenever possible, take one or two pictures of infested branches to help confirm identification. To avoid spreading hemlock woolly adelgid, do not collect sample branches or twigs.

The MISIN smartphone app will take a GPS location point if a report is made at the site; it also will allow you to upload photos with a report.

The updated hemlock woolly adelgid interior quarantine is available online at Suspected quarantine violations can be reported by emailing For more information about invasive species in Michigan, visit


Michigan's Invasive Species Program is cooperatively implemented by the Department of Environment, Great Lakes, and Energy, the Department of Natural Resources, and the Department of Agriculture & Rural Development. 

Note to editors: The photos below are available for download. Caption information follows. 


Branch: An eastern hemlock tree branch infested with hemlock woolly adelgid.
Photo courtesy of Steven Katovich, USDA,


Ovisac: Tiny hemlock woolly adelgids build round, white ovisacs to protect their eggs.  Ovisacs are most visible from fall to spring on the underside of hemlock branches.
Photo courtesy of Lorraine Graney, Bartlett Tree Experts,

Map: Washtenaw County Hemlock Woolly Adelgid Interior Quarantine Area


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