Michigan’s Department of Agriculture and Rural Development says the spread of hemlock woolly adelgid along Lake Michigan is increasing. Native to East Asia, hemlock woolly adelgid is an invasive insect that attacks Hemlock trees, feeding on their sap and killing them between 4 and 10 years of infestation.

According to the MDARD, it’s been detected in Allegan, Antrim, Benzie, Leelanau, Manistee, Mason, Muskegon, Oceana, Ottawa, Van Buren, and Washtenaw counties. 

Rob Miller is the Michigan’s Department of Agriculture and Rural Development’s (MDARD) invasive species prevention and response specialist. Miller has played a crucial role in slowing the insect’s spread across the state. 

“Hemlock woolly adelgid really became a problem… between 2015 and 2017. It was [unintentionally] brought into the state on nursery stock that was infested with hemlock woolly adelgid [and] there are no native predators or diseases to keep [their] populations in check,” Miller says. 

While infestations have been found at the University of Michigan’s Nichols Arboretum, Miller is not overly concerned for Southeast Michigan. He says Southeast Michigan’s climate isn’t suited for hemlock trees, so the area doesn’t have a large population of them to worry about.

However, Miller is very concerned for the infestations detected in the west and northern regions of Michigan’s Lower Peninsula, where there are hundreds of hemlock trees. 

Treatment for hemlock woolly adelgid 

Unfortunately, Miller says the infestation is too far along and too widespread for eradication to be an option for MDARD. One way the state  is supporting this effort is by funding local conservation districts that have Cooperative, Invasive Species Management Area (CISMA) programs. Miller says this partnership gives local conservation districts more resources to directly treat and prevent hemlock woolly adelgid infestations. 

For property owners, there are two different insecticides to treat hemlock woolly adelgid infestations: imidacloprid and dinotefuran. 

Miller differentiates these chemicals by the speed they move through trees; imidacloprid moves slowly and protects the tree for longer, and dinotefuran moves quicker and protects the tree for a couple of years. 

Both insecticides are neonioctinoids, which are harmful among pollinators. However, Miller explains that application techniques reduces the environmental risk of these chemicals.

“You’re applying [insecticide to protect hemlock trees] either directly to the trunk of the tree or you’re actually injecting it in the tree. You’re not spraying it all over the place…shooting it out of a high pressure hose [or] using a mist system,” he says.”

“So, when it’s applied to the tree properly, it’s very targeted and that chemical is then actually inside the tree, and we don’t have any runoff.” 

This story is part of WDET’s ongoing series, The Detroit Tree Canopy Project.

Health experts and urban planners have long believed that planting more trees in residential areas is good for everyone in those neighborhoods.

A new study shows that’s not necessarily so.

Researchers at Michigan State University found that while trees do reduce stress and extend longevity, the benefits vary based on other factors.

Professor Amber Pearson led the study. She and her team examined the relationship between residential tree canopies and allostatic load. That’s the cumulative wear-and-tear that stress has on the human body. Pearson says they confirmed that trees improve human health.

“What we found was that having higher percentage of residential trees was associated with lower allostatic load scores,” she says. “In other words, it’s good for your health.”

But Pearson found something surprising: It wasn’t good for everyone.

Researchers used federal health data on 40,000 people across the country. They also looked at satellite data from tree canopies in about 10 million U.S. census tracts.

Pearson says health benefits varied based on things like education, income, and employment.

“We found a relationship in those that were more socioeconomically advantaged, but not the more vulnerable or disadvantaged participants,” she says.

The study found that Hispanic and non-Hispanic white participants saw significant improvement, while non-Hispanic Black participants did not.

Pearson says social and economic stress may override nature’s health benefits. 

“Trees alone may not be enough to overcome those stressors in those populations,” she says. “We really need to do more to understand those stressors and that’s an area of future research.”

Pearson says the findings could challenge people’s assumptions about trees.

“Trees are not a panacea,” she says.

The study appears in the Lancet Regional Health – Americas.

This story is a part of WDET’s on-going series, The Detroit Tree Canopy Project. 

The U.S. Forest Service is shutting down all four of its research centers in Michigan as part of a nationwide reorganization, sparking concerns about the future health of forests in the Great Lakes.

According to environmental advocates, the closure could increase problems like invasive pests and diseases, as well as harm wildlife, outdoor recreation, and forest biomes. 

Emma Shedd is with the Sierra Club’s Michigan Chapter. She says the importance of these research centers cannot be ignored.

“It is a big deal….there are a lot of impacts that we can expect to see [like layoffs and loss of skilled research staff]…we can [also] expect to see a much weaker agency, and that trickles down to a lack of regional research to support our forests here [in Michigan].” 

Researchers with the U.S. Forest Service study forest health, monitor invasive species, and collect long-term data that help both federal and state agencies make decisions. Shedd says this includes a nationwide program which guides actions about logging, wildlife habitats, water quality, and outdoor activities.

Without these facilities, she says, a lot of that work could be reduced or lost. 

Shedd says, “Forest management is a long term game…we’ve got rotations of 60 to 80 to 100 years going on in our forest, and so having a lack of management now…has effects that span whole lifetimes.” 

She says Michigan residents who oppose the drastic cuts to the U.S. Forest Service should call their representatives. “This is something that we really need to push back on for… the health of our forests in the long term,” Shedd says.

This story is a part of WDET’s ongoing series, the Detroit Tree Canopy Project.

Last October, Ground Services at Wayne State University discovered an infestation of bark beetles on trees in Gullen Mall. 

Donna Reincke, Associate Director of Grounds for Wayne State University, explains how these tiny insects caused great harm. 

“They burrow into the tree trunks and leave these tiny little holes, maybe about the size of a pencil eraser. With that, the insect infestation introduced a fungus [blue stain fungus] into the tree, which stopped the tree from being able to take up water, and killed a couple of the trees.”

The fungus spread to surrounding trees and left them too damaged to save.

Reincke says sadly, they had to remove 11 pine trees in Gullen Mall, as dead trees pose a major safety risk.

“We do remove them to avoid any accidents from happening, and it’s just a safety issue with the risk of it falling, and dead branches falling down,” explains Reincke. 

Expanding campus tree canopy

With the help of many volunteers from The Greening of Detroit and Wayne State University’s Office of Sustainability, Reincke is happy to share that they replanted 30 trees in the same area. 

Reincke says, “even though the trees are smaller than the ones that were removed, we wanted to make sure we still did right by planting trees that could fill in the canopy, and it was a really fun, successful event.”

In addition to Gullen Mall, Reincke stated they planted 71 trees at Wayne State University’s athletic complex, on the corner of Warren Avenue and Trumbull Street. 

Over these two spaces, they planted Hackberry, Kentucky Coffee ‘Decaf’, Bald Cypress, ‘Autumn Splendor’ Buckeye, Allegheny Serviceberry, London Plane, Blackgum, Tulip Tree, Basswood, Accolade Cherry, and Swamp White Oak. 

Wayne State University’s Ground Services and Office of Sustainability are partnering up again to host a tree planting event for Arbor Day, April 24th, 2026.

For more details, visit Wayne State University’s Get Involved page.