Surveys find large infestation of invasive hemlock woolly adelgid, prompting closures in Sleeping Bear Dunes National Lakeshore for treatment; pest, which can kill hemlock trees in four years, has been moving north along Lake Michigan coastline since 2015

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EMPIRE, MI - The Old Indian Trail and surrounding area in Sleeping Bear Dunes National Lakeshore (National Lakeshore) is closed due to invasive hemlock woolly adelgid.

Surveys this January and February found a large infestation on the southern boundary of the National Lakeshore, along and around the area of the Old Indian Trail. This infestation has prompted an area closure to slow the spread and allow for treatment. Plans are in development to reopen the trail by the fall of 2024.

This pest can kill hemlock trees in as little as four years. The insects access the tree's nutrients at the base of the needles, starving the tree. In the fall and winter, the adelgids cover themselves with a white, waxy coating for protection that appears as wool bundles the size of a pinhead at the base of hemlock needles.

The aphid-like insect has been moving north along the Lake Michigan coastline since 2015 and is known to be present in seven Michigan Counties: Allegan, Benzie, Mason, Muskegon, Oceana, Ottawa, and Washtenaw. It spreads by wind, on wildlife, and via humans on clothing, vehicles, and by moving firewood.

Since 2018, the National Lakeshore has conducted annual winter monitoring surveys in hemlock groves throughout the park.

A small infestation in a single tree was identified and treated in the Platte River Campground in 2022.

Those visiting the National Lakeshore - especially those coming from an area with known infestations - can help slow the spread by following these recommendations:

• Obey closures, stay on trails, and treat clothes and hiking equipment by machine drying on high heat after a hike.

• Do not park under low hanging branches and wash vehicles often when traveling between areas in the region.

• Learn how to identify Eastern hemlock trees and hemlock woolly adelgid.

• Report possible sightings to the National Lakeshore or Northwest Michigan Invasive Species Network.

• Use the citizen science app MISIN (Midwest Invasive Species Network) to post location-specific photos of HWA.

Hemlock trees are common in the National Lakeshore and throughout the region. These trees provide food, shade, and cover for many species of birds and mammals. They are especially important during the spring before other plants have grown back their leaves. Eastern hemlock trees often grow around freshwater rivers and streams. In these areas, their shallow roots help to stabilize the soil and limit erosion. The shade also keeps water temperatures cool for animals like fish and aquatic invertebrates.