If you’ve ever walked through Michigan’s northern forests there’s a great chance you might have seen an eastern hemlock tree. The trees are among some of the longest living trees in the entire state, and now they may need our help.
Hemlock woolly adelgid was recorded in Michigan for the first time in Ottawa County in 2015 . Since then, state and conservation organizations across Michigan have been on high alert to make sure the pest isn’t able to spread and destroy our hemlocks, and with them, our local ecosystems.
Up north, at the Little Traverse Conservancy, volunteer manager Cacia Lesh, is helping to organize and train volunteers to survey for HWA. The conservancy began partnering with CAKE CISMA, a Northern Michigan invasive species management organization, in 2019, to help train volunteers. The conservancy and CAKE CISMA currently have 10-12 volunteers that survey the preserves specifically for signs of HWA.
“Our volunteer program is vital, we can’t send one person to survey all of our properties so it’s incredibly important,” said Lesh. “The more we can do to protect unique species like the hemlock, the more we’re doing for our ecosystem.”
According to a Michigan.gov extension bulletin, HWA, or hemlock woolly adelgid, is a small aphid-like insect native to Japan. It’s not very new to North America, and in the Western U.S. it’s a normal part of the forest ecosystem. It was first found in the Eastern U.S. in 1951 in Virginia where it was considered a pest. According to Michigan.gov’s invasive species watchlist, HWA has already spread to 20 eastern states, including Michigan, threatening to decimate massive populations of native hemlock trees.
“We believe it most likely came into Michigan through nurseries selling trees carrying HWA from other states,” said Deb McCullough, a Michigan State University professor and forest insect ecology and management expert. “Because of that there’s been a quarantine since 2020 on infected hemlock trees coming into Michigan.”
McCullough says that even though the adelgid can’t fly and barely moves once it begins to feed, it can still hitch a ride on birds, animals, and even us so the state and conservation organizations need to be diligent about keeping HWA out of Michigan.
“We have insecticides that are able to control the adelgid on a small scale,” said McCullough. “But when you’re talking about out in the woods, we have something like 173 million hemlocks and obviously that’s not gonna work, the scale is just too big.”
According to the USDA, Hemlock trees are coniferous trees distinguishable by their short, flat pine needles. They can grow 70-100 feet tall and can live more than 800 years. McCullough said they can also do a lot for the ecosystems they occupy.
“It’s ecologically important because it’s a foundational species,” said McCullough. “It provides really important wildlife habitats. In the summer it provides shade and in the winter it provides cover for many animals.”
Not only do they directly affect Michigan wildlife, but the environment too.
“Hemlocks often grow next to streams, rivers, and lakes,” said McCullough. “They have a really strong influence on water quality, and huge impacts in nutrient cycles both in the soil and water. When the hemlocks are killed by the adelgid it can have profound impacts on the environment around it”
One of the few things keeping HWA at bay is cold weather.
“Hardly no insects feed in the winter, but this one does,” said McCullough. “If it gets cold enough you can get really high rates of mortality for the insects which is great.”
As yearly temperatures increase, McCullough warns that climate change could have a drastic impact on the adelgid’s mortality rates.
“It’s profound how much lower Michigan is expected to be warmer in the future,” said McCullough. “This poses an even greater threat of the adelgids, you can definitely expect them to spread.”
While warmer temperatures may be hard to avoid, there are many other organizations looking to slow the spread of HWA any way they can.
Jack Polus is a seasonal field crew member at the Grand Traverse Regional Land Conservancy and he said he believes the conservancy is doing their part to maintain the spread of HWA.
“In our profession, we’re the boots on the ground and we’re gonna be the ones who find it and hopefully treat it,” Polus said.
Polus says that if the right precautions are taken, there’s time for a solution, especially on smaller scales.
“It’s relatively slow moving and can take several years for the adelgid to actually kill the tree,” said Polus. “From a landscaping perspective, it’s manageable.”
Anyone can help do their part to slow the spread of HWA too.
Audrey Menninga, an invasive species specialist at the Northwestern Michigan Invasive Species Network, outlined some of the ways anyone can help identify and fight against HWA in a Jan. 15, 2021 webinar.
“What you’re looking for is random dying branches,” said Menninga in the webinar. “Some heavily infested trees can get a lime green color to them.”
According to the webinar, priority areas include parking lots, campgrounds, waterways and any high traffic areas.
Like Polus, Menninga is optimistic.
“We kind of have a head start on this,” said Menninga in the webinar. “This isn’t something that we’ve looked around and it’s everywhere, we do have a chance of controlling this.”
For more information of the woolly adelgid in Michigan, you can visit the state’s website. Anyone interested in volunteering against the spread of HWA should check in with their local nature conservancies or local invasive species organizations.