The Michigan Department of Natural Resources recently confirmed a new detection of invasive hemlock woolly adelgid at Ludington State Park in Mason County. These invasive insects can cause significant harm to Michigan’s hemlock resource, estimated at 170 million trees.
Hemlock woolly adelgids are tiny insects from Asia that feed on the sap of hemlock trees, spinning white, waxy ovisacs to protect their eggs. Over time, their feeding kills needles, branches and whole trees.
On Oct. 19, a single hemlock woolly adelgid adult and ovisac were found on a hemlock tree branch in a wooded area off a trail near the west shore of Hamlin Lake. This discovery is approximately 17 miles north of Bass Lake, where the first hemlock woolly adelgid infestation in Mason County was detected in March 2020, prompting the Michigan Department of Agriculture and Rural Development to extend its hemlock woolly adelgid internal quarantine in September.
The internal quarantine, which regulates movement of hemlock nursery stock, forest products and yard waste, now covers Allegan, Ottawa, Muskegon, Oceana and Mason counties, all bordering Lake Michigan.
Round, white hemlock woolly adelgid ovisacs are found on the undersides of branches near the base of the needles.
The single insect and ovisac were spotted by Travis Wilcox, a member of the Michigan Civilian Conservation Corps Forest Health Crew in the DNR’s Parks and Recreation Division, during a routine survey of the park’s hemlock forests.
“It was a cold, clear morning, and I had just completed a careful binocular survey of a large tree. I turned around to another, smaller hemlock and saw the ovisac right away,” said Wilcox. “We spend a lot of time looking at these trees. Anything white on the underside of a branch catches our attention.”
DNR Parks and Recreation Division has been managing hemlock woolly adelgid infestations in state parks since early 2017 when the insect was first detected at P.J. Hoffmaster State Park. MCCC crews may walk several thousand miles a year over rough terrain to survey, mark and treat trees in affected areas.
Due to its experience, the crew at Ludington was able to survey the surrounding area quickly and treat nearly 400 hemlocks in the vicinity to try to prevent the infestation from spreading or intensifying. Through survey efforts, four additional infested trees were identified.
Map showing the known infestations of hemlock woolly adelgid in Mason County, including Ludington State Park.
Ludington State Park is the eighth state park where hemlock woolly adelgid populations have been found, and currently the northernmost point of infestation. Eastern hemlock trees are an integral part of Michigan’s coastal dune ecosystem, which stretches along the state’s west coast into the U.P. Hemlocks are also found in Michigan’s northern hardwood forests.
MCCC crews will continue survey work in state parks throughout the winter, when ovisacs are most visible. Additional surveys will be conducted by Cooperative Invasive Species Management Areas in coastal areas along Lake Michigan.
Hemlock woolly adelgids can be carried to new locations, sometimes miles away, by birds, wildlife and even wind. This new detection so far away from other known infestations highlights the importance of regular surveillance of hemlock trees.
How can you help?
Residents with hemlock trees on their properties and anyone visiting forested areas this winter can assist in this effort by taking time to look at the undersides of hemlock branches for evidence of hemlock woolly adelgids. Birders with binoculars can be especially helpful in spotting the invasive pest.
What to look for:
Late fall through early spring is the best time to check hemlock trees. Look on the undersides of branches for evidence of round, white ovisacs near the base of the needles.
Up close, ovisacs look like balls of spun cotton and may appear alone or in clusters. The short video Hemlock Woolly Adelgid: Invasive Species in Michigan provides helpful identification tips.
Other, less damaging pests easily can be mistaken for hemlock woolly adelgids. Be sure to review photos and descriptions of common hemlock woolly adelgid look-alikes at Michigan.gov/HWA. Help in identifying eastern hemlock trees is also available at the same site.
How to report:
Trees infested with HWA should be reported by one of the following means:
- Email the Michigan Department of Agriculture and Rural Development at MDA-Info@michigan.gov.
- Call the MDARD Customer Service Center at 800-292-3939.
- Use the Midwest Invasive Species Information Network (MISIN) online reporting tool.
- Download the MISIN smartphone app and report from your phone.
Be prepared to report the location of infested trees and, whenever possible, take one or two pictures of infested branches to help confirm identification. To avoid spreading hemlock woolly adelgid, do not collect sample branches or twigs.
The MISIN smartphone app will take a GPS location point if a report is made at the site; it also will allow you to upload photos with a report.