Stopping a Tree Killer – The Race to Control Hemlock Woolly Adelgid

Hemlock Woolly Adelgid “ovisacs.”

Up and down the west side of Lower Michigan, small armies of natural resource professionals and conservation volunteers are scouring the woods and tromping through deep snow searching for killers … infestations of tiny aphid-like insects that suck the life out of Eastern Hemlock trees:  the Hemlock Woolly Adelgid.

In this video, Shaun Howard, project manager for The Nature Conservancy (TNC) explains that the Hemlock Woolly Adelgid (HWA) is a small aphid-like insect that feeds on hemlock trees by extending a proboscis-like appendage into the base of leaves. This tiny tree-killing insect reproduces asexually, laying as many as 300 eggs each, annually. With such exponential population growth, these tiny insects can suck the nutrients and life out of a tree within a few years.

Shaun Howard

An invasive pest imported from Asia decades ago, HWA has attacked and killed whole hemlock forests in the eastern United States from Maine to the Carolinas. Experts believe the insect was first imported into Michigan with infested nursery stock in 2006. Though the first small infestations were eradicated with pesticides, HWA has invaded the forests of West Michigan, including popular state parks.

In this video we learn about recent efforts to stop this invader through extensive winter survey work to locate infested trees by looking for the small white woolly masses that appear on underside of hemlock stems and leaves. According to Natural Resources Steward Heidi Frei (Michigan Department of Natural Resources) these white masses or ovisacs are present in the winter and are the most visible sign of infestation. So, winter is the best time to look for signs of infestations. Once detected, the trees can be treated to kill the insects during the growing season.

Heidi Frei

Though HWA has infected hemlock trees in many locations along the west side of Michigan, the impact remains relatively contained to a few counties. Further, there are good chemical treatments that can be used to kill HWA efficiently. That’s why Katie Grzesiak, Coordinator for the Northwest Michigan Invasive Species Network believes that this invasive pest can be stopped.

As Grzesiak points out, there are no known occurrences of HWA in Northwest Lower Michigan. Further, ISN’s team is very active surveying hemlocks throughout the area. With help from a large number of nonprofit organizations and local agencies, even more survey work is getting underway.

Katie Grzesiak

People who own hemlock trees are encouraged to inspect their trees this winter for signs of HWA. Sightings should be reported as soon as possible to either the Midwest Invasive Species Network or the Michigan Department of Agriculture and Rural Development.

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