Article written by: Nealy Molhoek, Stewardship Supervisor

As hints of spring begin to appear all around us, many of us take the opportunity to spend more time outdoors, either in our own backyards, or in the parks that we’re so lucky to be surrounded with in Ottawa County.

However, not all signs of spring are positive. Many prolific invasive plants actually start to grow new foliage before their native counterparts. Additionally, the warmer temperatures bring seasonal risks of spread for forest pests and threats like hemlock woolly adelgid (HWA) and oak wilt. Both of these forest threats are being considered and closely monitored in Ottawa County Parks. HWA in particular is a high priority for Parks Natural Resources Management staff.

Hemlock Woolly Adelgid (HWA) is a forest pest that has been destroying hemlock forests in the eastern US for almost fifty years. Since its first recorded infestation here in Michigan, it has been found in at least eight Counties, from Berrien County in Southern Michigan, and recently, all the way up to Benzie County in Northwest Michigan (with an isolated population in Emmet County). It tends to spread more quickly along bodies of water, using birds and their flyways as vectors, or modes of spread. Lake Michigan is an important flyway, and therefore a route of spread here in Michigan. In Ottawa County, the majority of known populations of HWA are located in forests along the shores of Lake Michigan. This concentration is due partially to the proximity to the aforementioned flyway, but also the greater numbers of hemlock stands in these forested dune ecosystems.

Within the parks system, we are working to survey every hemlock tree in our 7,000+ acres, prioritizing treatment in areas where HWA is known to already exist or exist nearby. To protect these ecologically important trees from the impacts of HWA, we apply a systemic insecticide that will stay active within the vascular tissues of the tree and control the destructive insects for at least five years.  Parks staff, volunteers, and interns started treatments for HWA in 2019. Between 2019 and now, OCPR has treated 2,814 of the most imperiled hemlock trees in the Parks system. Staff and interns are currently working to survey, and collect important data from, the hemlocks at the 164-acre Rosy Mound Natural Area. HWA treatments at Rosy will start in June of 2022.

OCPR Staff and Interns Surveying Hemlocks at Rosy Mound Natural Area

OCPR Staff and Interns Surveying Hemlock Trees at Rosy Mound Natural Area

For more information about HWA, please visit West Michigan Hemlock Woolly Adelgid Taskforce’s website at or check out the State of Michigan’s HWA information site. For information about upcoming stewardship volunteer events and helpful educational programs; including one at the end of April that will discuss aspects of managing for oak wilt, take a look at the West Michigan Conservation Network‘s events calendar.

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