Mold Remediation in Hemlock, MI

VAN BUREN COUNTY, Mich. — The Michigan Department of Agriculture and Rural Development (MDARD) announced Tuesday they have confirmed new detections of invasive hemlock woolly adelgid in 11 of the state's counties.

In Van Buren County, forest health technicians with the Michigan Department of Natural Resources (DNR) Parks and Recreation Division found two hemlock trees infested with invasive hemlock woolly adelgid in Van Buren State park on March 3, officials said.

"Hemlock woolly adelgid is a small insect that uses its long, siphoning mouthparts to extract sap from hemlock trees," MDARD said. "This feeding weakens needles, shoots and branches. Over time, tree growth slows, and trees take on a grayish-green appearance. Without treatment, infested trees die within four to 10 years."

Technicians are in the process of determining the full extent of the infestation and are planning to treat the infested trees this summer, according to officials, who are advising park visitors to stay on designated trails to prevent any further spreading.

MDARD said there have also been confirmed infestations in the following counties:

To identify invasive hemlock woolly adelgid, MDARD said to look on the undersides of hemlock branches for round, white ovisacs --which resemble tiny cotton balls-- near the base of the needles. They may appear alone or in clusters.

MDARD provided the following options for those who wish to report any suspected infestations:

More information about invasive hemlock woolly adelgid and other invasive species in Michigan, and to find out what you can do to prevent them, can be found here.

(Today’s MI Environment story by Zoi Goss, of the Michigan Department of Natural Resources’ Forest Resources Division, is courtesy of the DNR.)

Well before sunrise on a Wednesday morning, I got up to make the journey from Lansing to Ludington to survey trees for an invasive insect known as hemlock woolly adelgid. The weather was in the 40s with a chance of rain, which, thankfully, held off until my drive home that afternoon.

At the site, I met up with a four-person crew from the West Michigan Conservation Network to get started surveying the woodland outside of West Shore Community College near Ludington.

Surveying means going through the woods to check each hemlock tree for signs of the tiny, invasive insect. If found, each infested tree is tagged and recorded for later treatment.

The crew I joined for the day is based in West Michigan, and they are called to check private and public lands for any signs of infestation. They have been in the woods all winter, checking new sections of hemlock forest for the adelgid, and I was able to join them to learn more about the process and what this insect is exactly.

Even though it was 40 degrees, snow still covered the ground, up to my knees in some spots! It was very pretty to be hiking around snow-covered trees and hearing the woodpeckers tapping above us in the branches.

We had been hiking through the woods for a few hours that morning, double-checking some trees that were marked as positive in a previous survey, but we hadn’t found any positive identifications.

Just as I was remarking that finding evidence of an infestation would be bad, but good for my article, one of the team members grabbed a branch and turned it over to look at the underside of the needles.

There it was – one tiny hemlock woolly adelgid attached to the branch and covered in its white protective mass. I had never seen a hemlock woolly adelgid – or any type of adelgid – in real life. It was interesting to see the team identify it and differentiate it from other, similar insects such as spittlebugs by examining the white covering.

What is this insect?

Hemlock woolly adelgid, or HWA, is an invasive species that was first confirmed in Michigan in 2006 and is currently found in 11 counties, mostly along the Lake Michigan shoreline.

This insect moves from tree to tree, transported by people, birds, animals or the wind. Once on a tree, it feeds on the sap of young branches at the base of needles.

This little thing is less than 1/16 inch long, nearly invisible to the naked eye and found most commonly in its mature stage, with a white, woolly, waxy protective covering that makes it stand out against the branch.

Adelgids lay their eggs on the branches and feed on the sap through the winter and spring. In summer, an infected hemlock experiences reduced branch growth, premature needle dropping, dieback and eventually death.

HWA is especially threatening to Michigan because the state is home to over 170 million eastern hemlock trees. These trees create shelter for birds and animals, stabilize soil near streams and regulate microclimates for fish and animals throughout the year.

Hemlock woolly adelgids currently affect over 20 states across the United States and at least two Canadian provinces.

Battling HWA takes teamwork

The Michigan Invasive Species Program, a joint effort of the Michigan Department of Natural Resources and the Michigan departments of Agriculture and Rural Development and Environment, Great Lakes and Energy, continues to work with Michigan State University and multiple local cooperative invasive species management areas, or CISMAs, to prevent the northward spread of HWA and protect high-quality ecosystems, including those in state parks along the Lake Michigan shoreline.

These groups work together to manage HWA by surveying forest sites during the winter to determine which areas are affected. Winter is the best time to survey because HWA is less likely to be spread to other trees in the area from human movement, and the egg masses are most visible in the winter.

The trees infested by HWA are treated in the summer, when the sap is flowing. Insecticide is injected into the sapwood of larger trees or sprayed onto the trunks of smaller trees.

The insects ingest the insecticides through the sap, and there is virtually no damage to the tree or surrounding plants. The treatments are effective for five to seven years.

Going out in the field is always exciting for me, as I spend most of my days behind a desk. I am not sure what I was expecting, but working in the field with the West Michigan Conservation Network HWA crew was a lot tougher than I thought.

Walking around for hours through the woods is so serene and peaceful, seeing all the trees covered in snow and guessing which animal left which prints behind. However, hiking through the snow is no easy task.

While I was tired and sweating, the crew was working along with no problem, enjoying themselves and surveying the trees. The work that they put in each day to protect our trees is incredible.

The team of four had a system figured out.

One person measured the trunk of the tree being examined to see how many holes they will have to drill in the spring. Another person tagged the tree with a number to catalog it. And yet another person checked the branches for HWA, while the fourth team member recorded all the information on an online survey data app.

The team is called to check sections of public and private lands in areas that are at risk for HWA.

There are treatment options for the insect and ways to help prevent its spread as well.

On your own land, you can prune branches that might hang low enough to hit vehicles driving by or parked underneath, as the insects can be transported long distances by vehicles.

You should clean your vehicle after traveling to make sure you do not accidently transport any invasive species. Cleaning your boots and equipment is another way to prevent accidental transportation.

If you think you see HWA, take a photo and report it so it can be identified, and action can be taken if needed.

Invasive species like HWA are everywhere and can be extremely dangerous for Michigan’s ecosystems.

We can continue to help fight against them with the help of CISMAs across the state and other DNR partners. You can help by being aware of the signs and symptoms of invasive species invasion.

The DNR and the Midwest Invasive Species Information Network have information on identifying and reporting different invasives.

It is better to be safe than sorry – if you think you see an invasive species, take pictures and report it right away. Find more information on species identification and reporting at MISIN.msu.edu or Michigan.gov/Invasives.

After my day in the woods with the survey crew, I got home that night and was exhausted. I got in all my steps and had sore legs to prove it for the next few days.

Being in the field is the best part of my job. I get to more fully understand and appreciate Michigan’s natural resources and the people whose job it is to protect them.

This trip was also fun and informative because you always hear about all these invasive species, but you don’t always get to go out and see them up close, nor do you get to accompany the people who are fighting their spread and destructive impacts.

Going forward, I am now looking forward to learning about more invasive species and what we all can do to battle them.

Department of Environment, Great Lakes, and Energy Department-wide MI Environment Invasive species

Zoi Goss

Communications representative

Forest Resources Division

Michigan Department of Natural Resources

GossZ@Michigan.gov

MI Environment Team

EGLE-Assist@Michigan.gov

517-284-9278

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If hemlock trees on your property show signs of hemlock woolly adelgid infestation, now is a good time to plan for spring treatment of this invasive species. Hemlock woolly adelgid, native to Asia, is known to be present in areas of Allegan, Antrim, Benzie, Leelanau, Manistee, Mason, Muskegon, Oceana, Ottawa, Van Buren and Washtenaw counties in Michigan. These small insects suck sap from hemlock needles and ultimately can cause tree death.

Insecticides are available to control the insect, and in many cases, landowners can apply them easily by carefully following label instructions and application rate guidance. In Michigan, the label is the law. Due to certain restrictions on the use of these insecticides, you may need the services of a licensed pesticide application business.

If one or more trees are infested, make plans to act this year. Without treatment, trees infested with hemlock woolly adelgid are likely to die within four to 10 years. Weakened trees on a home landscape could spell disaster during high winds or storms, and eventually they will have to be removed. Loss of hemlocks in forested areas can reduce shade, winter cover, and food and habitat for birds, fish and mammals.

Leelanau Branch of Hemlock Wooly Adelgid

Which treatments work?

Products containing either imidacloprid or dinotefuran as the active ingredient and labeled for treatment of hemlock woolly adelgid are effective in combating the insect.

No matter which treatment you select, be sure your treatment plan includes all hemlocks on your property over the next few years. If hemlock woolly adelgid is on your site, hemlocks without symptoms are very likely to be infested over time, including trees on neighboring properties. It’s a good idea to discuss treatment plans with neighbors and coordinate efforts when possible.

Can I treat trees myself?

Application of imidacloprid or dinotefuran is simple enough for many landowners to do themselves. Products containing these chemicals are available at garden supply stores, packaged under various trade names in liquid or granular form. Check the label or ask for assistance in selecting the right product.

Imidacloprid and dinotefuran products available at garden supply stores generally are applied to the soil close to the tree trunk, where they are absorbed through the root system. Plan your application for a time between early April and late October, when the ground has thawed and soil moisture is moderate – not too dry or saturated. The sooner you treat, the more successful your treatment will be.

Follow all label directions, wear appropriate safety gear and determine the right application rate to ensure positive results. To protect the environment, do not allow the product to enter or run off into storm drains, drainage ditches, gutters or surface waters.

Some products have restrictions on the amount that can be applied to an area per year. Be sure to read the label carefully to determine if the amount you need falls within these limits. If not, you may need to adopt a multiyear plan or hire a professional.

More information on do-it-yourself treatment can be found in the Michigan State University Extension bulletin Guidelines for homeowner treatments of hemlock trees infested with hemlock woolly adelgid.

When should I call a professional?

Licensed pesticide application businesses have a broader range of options for applying treatments than consumers, and their professional skills are recommended in certain situations. A county-by-county list of businesses holding pesticide application licenses can be found on the Michigan Department of Agriculture and Rural Development’s website, Michigan.gov/MDARD. For lawn or landscape trees, look for a professional licensed in the ornamental category (3B); for forest trees, choose the forestry category (2).

If your hemlock trees are within 75 feet of a body of water or in areas with a high water table, or if flowering plants or shrubs are growing around the hemlocks you wish to protect, a trunk injection or bark treatment may be necessary to avoid affecting the environment, groundwater or other insects. Professional applicators can provide these types of treatments.

What should I expect after treatment?

Hemlock woolly adelgid’s cottony, white ovisacs will linger for a time following treatment. If trees are treated in the spring with dinotefuran, check new growth in late fall or winter for any fresh signs of infestation. With imidacloprid, wait until a year after treatment to gauge effectiveness.

After treatment, trees should be checked every year. If the insect has returned after dinotefuran was used, reapplication may be needed after one to two years. For imidacloprid, consider retreatment every four to seven years.

Do my trees have hemlock woolly adelgid?

If you have hemlock trees on your property, it is important to check them for signs of hemlock woolly adelgid, which infests only hemlock trees. If you are not sure whether your trees are hemlocks, use the Michigan Invasive Species Program’s eastern hemlock identification guide.

The adelgid’s round, white, cottony ovisacs are most visible in the winter and are located on the undersides of hemlock branches at the base of the needles. The publication Hemlock Woolly Adelgid Look-Alikes, available at Michigan.gov/HWA, provides images and information on identifying this and other pests commonly mistaken for it.

How do I report an infestation?

If you suspect trees on your property have hemlock woolly adelgid, report it using the Midwest Invasive Species Information Network at MISIN.MSU.edu. You can report from the field using the MISIN smartphone app, which will log the location and allow you to upload photos of the suspected signs of the insect.

You also can take pictures, note the tree’s location and email the information to MDARD at MDA-Info@Michigan.gov or report by calling 800-292-3939. Someone will respond to let you know if hemlock woolly adelgid is present or not.

Please do not clip infested branch samples and transport or mail them. This could accidentally spread the insect to new areas.

For more information on identifying and managing hemlock woolly adelgid, visit Michigan.gov/HWA.

Michigan's Invasive Species Program is cooperatively implemented by the Michigan departments of Agriculture and Rural Development; Environment, Great Lakes, and Energy; and Natural Resources.

Department of Environment, Great Lakes, and Energy Department-wide MI Environment Invasive species

Joanne Foreman

ForemanJ@Michigan.gov

517-284-5814

Erin Briggs

BiggsE1@Michigan.gov

231-519-8312

MI Environment Team

EGLE-Assist@Michigan.gov

517-284-9278

With the threat of hemlock woolly adelgid infestations growing the Michigan DNR is urging residents who have hemlock trees on their property to plan for spring treatment of this invasive species.

Hemlock woolly adelgid, native to Asia, is known to be present in areas of Allegan, Antrim, Benzie, Leelanau, Manistee, Mason, Muskegon, Oceana, Ottawa, Van Buren and Washtenaw counties in Michigan. These small insects suck sap from hemlock needles and ultimately can cause tree death.

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Insecticides are available to control the insect, and in many cases, landowners can apply them easily by carefully following label instructions and application rate guidance. Due to certain restrictions on the use of these insecticides, you may need the services of a licensed pesticide application business.

Treatment Plans

The Michigan DNR noted that treatment plans that work include the use of either products that contain imidacloprid or dinotefuran as the active ingredient and labeled for treatment of hemlock woolly adelgid.

Imidacloprid moves slowly through trees, taking at least a year to reach the top of a large tree. However, one application will protect the tree for at least four years.

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Dinotefuran moves through hemlock trees more quickly, making it ideal for heavily infested trees. Dinotefuran protects trees for one to two years.

They note that whichever treatment plan is selected, be sure to include all hemlocks on the property. They state that if hemlock woolly adelgid is on your site, hemlocks without symptoms are very likely to be infested over time.

The Michigan DNR notes that the application of imidacloprid or dinotefuran is simple enough for many landowners to do themselves. Products containing these chemicals are available at garden supply stores, and packaged under various trade names in liquid or granular form. Check the label or ask for assistance in selecting the right product.

Imidacloprid and dinotefuran products available at garden supply stores generally are applied to the soil close to the tree trunk, where they are absorbed through the root system. Plan your application for a time between early April and late October, when the ground has thawed and soil moisture is moderate – not too dry or saturated. The sooner that the tree is treated, the more successful the treatment will be.

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Some products have restrictions on the amount that can be applied to an area per year. Be sure to read the label carefully to determine if the amount you need falls within these limits. If not, you may need to adopt a multiyear plan or hire a professional.

If the hemlock trees are within 75 feet of a body of water or in areas with a high water table, or if flowering plants or shrubs are growing around the hemlocks you wish to protect, a trunk injection or bark treatment may be necessary to avoid affecting the environment, groundwater or other insects. Professional applicators can provide these types of treatments.

The Michigan DNR said that hemlock woolly adelgid’s cottony, white ovisacs will linger for a time following treatment. If trees are treated in the spring with dinotefuran, check new growth in late fall or winter for any fresh signs of infestation. With imidacloprid, wait until a year after treatment to gauge effectiveness.

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After treatment, trees should be checked every year. If the insect has returned after dinotefuran was used, reapplication may be needed after one to two years. For imidacloprid, consider retreatment every four to seven years.

March 25, 2025

Reporter

Brendan Sanders is a 2022 graduate of Ferris State University with a bachelor's degree in sports communication and minors in journalism and marketing/sales. At Ferris State he was the editor in chief for the Ferris State Torch newspaper and is a member of Ferris State University's Sports Leadership Institute Advisory Board. A Lowell High School graduate, Brendan is an avid fan of various sports, including football, basketball and any form of motorsport.