Associated Press

LANSING, Mich. — A new report says invasive species continue to pose one of the biggest challenges to the health of Michigan woodlands.

The Department of Natural Resources has released an updated assessment of the state's roughly 20 million acres of forest land. It examines threats such as insects, diseases and overall forest decline.

The report describes the DNR's efforts to control oak wilt, a danger to red oak trees. In cooperation with the U.S. Forest Service, tens of thousands of feet of root graft barriers have been created that prevent wilt from moving to healthy trees.

Also discussed in the document is the battle against the hemlock woolly adelgid, an invasive insect that kills hemlock trees. It was found in the west-central Lower Peninsula last year.

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