Visitors to Sleeping Bear Dunes National Lakeshore won’t be hiking on one of the park’s popular trails this summer.

The National Park Service (NPS) announced on Friday that the Old Indian Trail “and surrounding area in Sleeping Bear Dunes National Lakeshore” would be closed until fall, due to the presence of hemlock wooly adelgid (HWA). According to an NPS press release, a “large infestation” of HWA was discovered this winter “on the southern boundary of the National Lakeshore, along and around the area of the Old Indian Trail.”

HWA is an invasive aphid-like insect that, despite being native to Asia, found its way to North America in the 1950s and has been spreading ever since. Infestations of the trees in hemlock trees or spruce trees can quickly drain those trees of important nutrients. HWA suck the sap out of the trees, literally starving them. An infestation severe or long-running enough can cause needle loss, stunted tree growth, and eventually, death of the infested tree or trees. An HWA infestation can kill a hemlock tree “in as little as four years,” the press release reports.

Per the NPS, HWA “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. (The affected section of the National Lakeshore is located in Benzie County.) HWA has been able to continue its spread thanks to wind, wildlife, and humans. People often unknowingly spread the pest on their clothing, their vehicles, or things like firewood.

Since 2018, Sleeping Bear Dunes has been on high alert for HWA, conducting “annual winter monitoring surveys in hemlock groves throughout the park.” In 2021, one of those surveys clocked the first-ever HWA sighting within the National Lakeshore: a “small infestation in a single tree” at the Platte River Campground. The Old Indian Trail infestation is the second found in the park – and so far, the biggest. The closure of the area is intended to slow the spread of the invasive species and to allow park staff time to treat the infestation. According to the NPS, “plans are in development to reopen the trail by the fall of 2024.”