Hemlock trees help maintain a healthy forest ecosystem and are an important resource for wildlife that rely on dense hemlock canopies for winter cover and food. With more than 170 million hemlock trees in Michigan, HWA has the capacity to devastate the forests.

These aphid-like insects have specialized mouthparts that allow them to pierce the base of hemlock needles and suck out nutrients meant for the tree. Over a period of four to 10 years, hemlock trees will usually die from an HWA infestation.

While the threat has remained highest in the eastern United States, HWA has started moving into the Midwest, with sightings reported in southwest Michigan. There is concern the insect may hitch a ride across the lake to the Upper Peninsula, so WRISC’s survey efforts have been targeting the Lake Michigan shoreline. If spotted in the Upper Peninsula, the spread likely would be slow, as studies show cold winter temperatures can increase HWA mortality.

The public can look for any small, white, cotton-like ovisacs at the base of the needle. To help prevent the spread of HWA and other invasive species, don’t move firewood from place to place and keep equipment and clothing free of seeds and outside debris.

Connecticut Agricultural Experiment Station/Bugwood.org photo Branches of a hemlock tree shows hemlock woolly adelgid, an invasive species. The Wild Rivers Invasive Species Coalition surveys for HWA during the winter months, as HWA produces waxy ovisacs at the base of needles that are easy to spot.

To learn more about HWA, go to WRISC’s website at www.wrisc.org, or www.michigan.gov/invasives.

Wild Rivers Invasive Species Coalition is a cooperative invasive species partnership operating in Dickinson, Menominee, Florence, Forest, and Marinette Counties. They are dedicated to the management of invasive species on lands and waters through cooperation, education, prevention, and control.