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County pursues HWA treatment at area parks

Alexander Sinn • Jun 13, 2019 at 11:00 AM

An invasive pest that kills hemlock trees has arrived in Michigan and taken hold at multiple parks in Ottawa County.

Ottawa County Parks has established a management plan to limit the spread of hemlock woolly adelgid (HWA). The county has opted for injections of a pesticide in high-risk areas of two parks, a treatment they say is effective for 3-5 years.

The parasite was first discovered in 2015 at Historic Ottawa Beach Parks, which include Black Lake Boardwalks, Mount Pisgah and the Lake Michigan beach adjacent to Holland State Park. HWA was most recently detected at North Ottawa Dunes this past April.

At North Ottawa Dunes, trees within a buffer zone of 800 feet will receive the application this year, which includes nearly 15 acres. About 3 acres of Historic Ottawa Beach Parks will receive treatment, including 30 trees outside the buffer zone.

The parasite is also “widespread” at P.J. Hoffmaster State Park in southern Muskegon County, where it was detected in every survey thus far on the northern end of the park. The surveys are incomplete on the park’s southern end. More survey work will be undertaken at Hoffmaster this year.

No HWA was found at Olive Shores and Kirk Park, according to Ottawa County Parks officials.

Ottawa County Parks will get two injector systems from the West Michigan Cooperative Invasive Species Management Area for the treatments. The cost could vary widely, but materials are estimated to cost $835, while survey and treatment work is estimated at $1,248.

County officials said the application will be “highly targeted” and applied efficiently to use as little pesticide as possible. The chemical stays in the tree, officials said, and is not expected to leach into the sandy soils of these dune parks.

The City of Grand Haven is also pursuing a treatment plan for HWA at Duncan Memorial Park and Mulligan’s Hollow, where studies have indicated the pest is spread by human contact.

You can spot infected hemlock trees by looking for white, woolly masses attached to the tree at the base of the needle. Eastern hemlock trees have flat needles with two white stripes on their undersides.

To prevent the spread of HWA, do not immediately hike somewhere else after visiting a site known to have an infestation. Toss your hiking clothes in the dryer for 20 minutes to kill the parasites. When visiting parks, keep dogs on leashes to prevent them from picking up and spreading HWA.

For more information about regional efforts to fight HWA, report infected trees and get involved, visit savemihemlocks.org.

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