Hemlock woolly adelgid (HWA) is an invasive species now established in Ottawa County, as well as Allegan, Muskegon, Oceana and Mason Counties. HWA is an insect that targets hemlocks as their source of food. They can be found at the base of hemlock needles on the undersides of branches.

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. Report infested hemlock trees by using the Midwest Invasive Species Information Network, available online at MISIN.MSU.edu. Reporting infested trees, even if you will be managing them on your own, is important to help determine how far HWA has spread. This information also indicates where additional surveys may be needed.

Infested hemlock trees can be treated with specific insecticides to prevent HWA establishment or to destroy existing HWA. For more information on treatment options, contact the West Michigan CISMA Coordinator, Natalie Bekins, at natalie.bekins@macd.org or 616-414-2055.

The invasive pest can be spread by wind, mammals and birds, with birds being one of the primary ways HWA can move. Humans can also spread HWA through vehicles, trailers and campers that come in contact with infested trees and then move to a different location.

Ottawa County, along with Allegan, Muskegon and Oceana Counties, is a quarantine area for hemlock woolly adelgid. Movement of hemlock trees, boughs, firewood, logs or limbs is prohibited without a compliance agreement.

Assessing the health of your hemlocks

State of Michigan Woolly Adelgid Information