State expands quarantine to prevent the spread of hemlock-killing insect | Michigan Radio
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State expands quarantine to prevent the spread of hemlock-killing insect

Sep 21, 2020

Woolly masses about a fourth of the size of a cotton swab indicates a hemlock has been infested by the Hemlock Woolly Adelgid.
Credit Steven Katovich, USDA Forest Service, Bugwood.org

The state of Michigan is expanding quarantines to try to stop a pest from killing hemlock trees. Michigan’s 170 million hemlock trees are important because they help prevent erosion along streams and keep them cool, which helps fish habitat. The Michigan Department of Agriculture and Rural Development (MDARD) says hemlocks are also important to the timber and lumber industries, nursery and landscaping industries, the Christmas tree industry and the tourism industry.

The Hemlock Woolly Adelgid is the insect pest killing hemlocks in five counties along Lake Michigan: Allegan, Muskegon, Oceana, Ottawa, and Mason. It feeds on the starches of the trees.

"The hemlock woolly adelgid, a tiny sap-sucking insect related to aphids, is causing widespread death and decline of hemlock trees in the eastern United States. This species, native to Asia and the Pacific Northwest." -USDA Forest Service

“What you'll see are these white woolly masses. They're about one quarter the size of a cotton swab on the underside of branches and at the base of the needles. You'll see needle loss and branch dieback, gray tinted colored needles also. But the wooly masses are really the telltale sign,” said Jennifer Holton, director of communications for MDARD. The trees die in about five years or a little longer.

To keep the bug from spreading, the state is limiting how and where hemlock yard waste can be disposed. A quarantine has been updated to include Mason county, the most recently infested area. A compliance agreement is required of anyone moving yard waste including hemlock within the five counties. The yard waste must be securely transported and disposal sites must be at least 100 yards from any hemlock trees.

The updated quarantine also will require hemlock nursery stock be certified to be healthy before being shipped to Michigan.

“Now we're requiring out-of-state firms that are doing that. They have to provide information to MDARD in advance of shipping. That includes a plant health certificate from the state of origin and where it's actually goes,” Holton explained.

The expanded quarantines go into effect September 24.