The invasive plant species Spotted Knapweed is on the "most wanted" list and Oakland County Parks and Recreation is taking steps to get the infestation under control at Orion Oaks County Park.

"Our knapweed management plan is on a trial basis in the largest meadow area at Orion Oaks," Brittany Bird, natural resources technician, said. "In March a 22-acre section was burned, in June another 25 acres was mowed, and in July blunt knapweed flower weevils and root-boring weevils were released on 12 acres."

Knapweed is a three- to four-foot perennial that produces purple flowers late June-August. It is native to Europe and East Asia and was introduced to North America in the 1890s as a contaminant in alfalfa and hay seed. "Without any natural enemies, the plant spreads quickly," Bird said.

Portions of the 86-acre meadow field have up to 90 percent knapweed cover. Historic vegetation maps indicate the park was once grassland containing rare oak savanna.

"Our goal is to begin restoring the ecotype in the big meadow area to improve wildlife habitat and ensure the persistence of grassland birds and insects in the park," Bird said. "Removal of the knapweed and restoration of native prairie plants is integral to this effort."

The weevils were obtained from the Minnesota Department of Agriculture. Orion Oaks is one of three initial knapweed bioagent release sites in Michigan. Approval to release the
weevils was granted by the Michigan and U.S. Departments of Agriculture.

"Adult weevils, about a half inch or less in length, feed on the leaves and flowers May - August," Bird said. "The young larvae, called instars, feed on the seed heads of the plants and the root boring weevils prey on the roots. Oakland County natural resource managers will track the establishment and spread of the weevils throughout the meadow."

Orion Oaks County Park is bordered by Baldwin, Clarkston and Joslyn roads in Orion Township. For more information on natural resources stewardship efforts, please contact Bird at 248.858.1726.