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Hemlock Woolly Adelgid

Early Detection Saves Trees

Overview

Hemlock Woolly Adelgid (HWA) is an invasive insect that threatens eastern hemlock trees. The forest pest feeds at the base of the needles, draining the tree's stored nutrients and gradually weakening it. Without treatment, infested eastern hemlocks become unhealthy, their needles turn gray, and they can die within 4 to 10 years.​ HWA has been spreading along the western Michigan coast for several years, with confirmed infestations in seven counties. Early detection is crucial—identifying an infestation quickly allows for timely treatment, which can save affected trees and stop the spread into new areas. Thanks to funding from the Michigan Invasive Species Grant Program and the U.S. Forest Service, we are offering free HWA surveys in high-risk areas. To schedule a survey please fill out our survey consent form - linked below. 

Winter Surveys

HWA surveys are conducted in the winter for several reasons. First, the adelgids are most visible in the winter when cooler temperatures trigger feeding activity. As the adelgids feed they secrete a white, waxy substance that forms a round ovisac around them making the tiny insects easier to see. Additionally, the insects are only mobile in the spring and summer. Winter surveys ensure we're not inadvertently spread HWA from one site to another. 

If you live or own property within the orange area on the map you qualify for a free HWA survey from us. Residents outside of this area of focus are still welcome to sign up, and will be notified if there is additional time at the end of the season to survey their property. The orange area was selected because it's the most likely place for HWA to exist within our region. 

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Learn about HWA

Hemlock Woolly Adelgid (HWA) is native to Japan where it feeds on Asian species of hemlock and spruce trees. In its native range HWA is not a major pest issue because Asian hemlock species are fairly resistant to HWA and predatory insects are accustomed to feeding on the adelgids. In North America the Eastern Hemlock tree (Tsuga canadensis) is highly susceptible to HWA attacks in part due to little genetic resistance within the tree and also because of lack of predators. North American spruce tree species are not susceptible to HWA damage. 

How do I Identify HWA? 

HWA are tiny insects that are difficult to see without magnification. However, as the adelgids feed, they secrete white, fluffy strands of wax from pores on their body. This wax — called an “ovisac” — covers the adelgids, protecting the insects and their eggs from desiccation and natural enemies. The white ovisacs are most visible from late fall through early summer and can be found on the undersides of tree shoots. Their prevalence during the winter months makes this the easiest time of year to spot them. Additionally, adelgids always attach at the base of the needles, where the needle stem connects to the branch.

Hemlock Woolly Adelgid

How do I Identify an Eastern Hemlock tree? 

  • Location: Found in shaded, moist environments across the northeastern U.S., including parts of the Great Lakes and Appalachian regions.

  • Size: Eastern Hemlocks can grow 40–70 feet tall, with some reaching 100 feet. They have straight trunks up to 2 feet in diameter.

  • Needles: Soft, flat, dark green needles with a whitish stripe on the underside. They are ¾ to 1 inch long and arranged in two rows along the twig.

  • Cones: Small, cylindrical cones, 1–1.5 inches long, hang down from branches and mature in the fall. (see fig. 2) 

  • Bark: Dark brown or gray, with shallow ridges that become scaly as the tree matures.

  • Shape: The tree has a pyramidal or conical shape, with horizontal branches that may droop at the tips.

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HWA Lifecycle

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Why are Eastern Hemlock Trees Important? 

One of our most beloved evergreens, the eastern hemlock (Tsuga canadensis) is also a critical part of our local ecosystems. Often found along ravines, hillsides, and stream banks, eastern hemlock offer habitat for wildlife and provide shade for streams, effectively lowering stream temperatures and increasing oxygen for fish and other aquatic species. Hemlocks provide aesthetic value and are loved by homeowners. It is estimated that Michigan is home to 170 million eastern hemlock trees. 

Water Quality

Eastern hemlock trees help improve water quality

Fishing

The unique conditions created by hemlock streams are important to many species of fish

Wildlife Habitat

Dense hemlock groves provide habitat to wildlife year-round

Biodiversity

Hemlock trees are important for biodiversity

Erosion Control

Hemlock tree roots hold streambanks in place and prevent erosion

Aesthetic Value

Hemlock trees are frequently used in landscaping

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About our surveys

CAKE CISMA conducts hemlock surveys on public and private properties. You may submit the digital consent form above or request a PDF to print and mail back to us. Our surveys are free for the 2024-2025 season thanks to grant funding from the Michigan Invasive Species Grant Program and private donations. If you value our work and wish to support us please consider donating to CAKE CISMA

When we arrive to survey we will call you to let you know we're at your property and to discuss any questions/concerns you may have about hemlock woolly adelgid. No news is good news, if we don't find anything during our surveys we will not contact you unless requested. ​If we do find a suspected HWA infestation we will collect a sample and send it to the  Michigan Department of Agriculture for confirmation. You will be notified if the detection is positive, and CAKE CISMA will serve as a resource for you regarding treatment options. Please DO NOT collect samples yourself. CAKE CISMA staff have the required training and permits to collect and ship invasive species material. 

  • What is a CISMA?
    Cooperative Invasive Species Management Areas (CISMAs) are partnerships of groups and individuals that work to address invasive species impacts on the environment, economy and human health within a defined region. By collaborating across jurisdictional boundaries, CISMAs work to leverage resources and overcome challenges associated with the prevention, early detection, response and control of invasive species. Each CISMA is governed by a steering committee and their priorities are identified within a strategic plan. CAKE CISMA was started in 2015, thanks to help from local conservation districts, environmental professionals, and the Michigan Invasive Species Grant Program (MISGP). Every county in the state of Michigan has a CISMA.
  • What does CAKE CISMA do?
    Our staff work across several areas of invasive species management. We focus on education, outreach, and restoration. We host educational events at schools, we do invasive species treatment days with local non-profits, and treat high priority invasive species throughout our 4 county area. Most often we work with terrestrial invasive species, but occasionally work with aquatic invasive species as well. For specific info on our projects check out our projects page.
  • Where does CAKE CISMA work?
    Anywhere in Charlevoix, Antrim, Kalkaska, and Emmet counties, including Beaver Island. We work with the Beaver Island Archipelago Terrestrial Invasive Species Program to jointly manage invasive species within the beaver island archipelago.
  • Who does CAKE CISMA work with?
    We work with 30+ partner organizations at the local, state, and regional level. We also work with private citizens to answer questions, serve as a resource, and treat high-priority invasive species on their property. Recently we've been working on projects with organizations like Tip of the Mitt Watershed Council, Little Traverse Bay Bands of Odawa Indians, and the Grand Traverse Regional Land Conservancy. We also go to area schools for lessons and field days and offer presentations about invasive species to local organizations free of charge.
  • How is CAKE CISMA funded?
    We are entirely grant funded. We are currently operating under grants from the Michigan Invasive Species Grant Program (MISGP) from the State of Michigan, and the Great Lakes Restoration Initiative (GLRI) through the EPA as well as several other grants. We occasionally apply for local community grants for specific projects.
  • How does CAKE CISMA choose what to work on?
    Previously, we've focused on treating what we call our: Top 5 Least Wanted Plants in Northern Michigan. This list of plants included invasive phragmites, black swallow-wort, Japanese/giant knotweed, asiatic bittersweet, and purple loosestrife. These plants were chosen for reasons like: they're not yet wide-spread, they're particularly harmful to the environment, etc. For the past few years we've been able to treat any of those plants for free for anyone in our service area. Currently, we're working on a 4-county wide prioritization map to help guide us when choosing which natural communities throughout northern Michigan need our help the most. This doesn't mean we'll stop treating our Top 5 Least Wanted, but rather that we want to focus where we can make the most difference. If you have an invasive species management project you'd like us to work on please contact our Education & Outreach Specialist, Katie at cakeedu@macd.org
  • I think I found an invasive species, what should I do?
    First, verify that it's an invasive species. Reference multiple photos, descriptions, habitat preferences and range maps. Many invasive species have "look-alike" plants that may be mistaken as invasive species. For help with ID check out the Midwest Invasive Species Network (MISIN) website or our ID reference cards on our site. Next, report it to us or use the MISIN application to report it yourself! We receive reports for species submitted via the MISIN app in our service area. We may be able to come treat the species for you, or suggest ways you can do it yourself.
  • Will CAKE CISMA treat invasive species on my property?
    It depends on the species and your property. We tend to focus our treatment on high priority habitats or on high priority species. High priority habitats are natural areas that may be under above average environmental stress, are particularly important to large-scale ecosystem function, or contain threatened/endangered species. High priority species are species within the CAKE service area that we've determined have the potential to cause extensive environmental degradation or may spread rapidly if left untreated. For example, we don't often treat Autumn Olive on private property, but we do treat Japanese Knotweed on private properties. If you'd like to know if your property qualifies for free or low-cost treatment contact us, our site visits are always free!
  • Does CAKE CISMA use herbicides to treat invasive species?
    It depends on the plant, location, and what the landowner prefers. CAKE CISMA uses the best management practices for each of the species we work to control in each habitat. Sometimes it is most effective and least environmentally detrimental to use chemical controls, sometimes biological controls work best, and sometimes mechanical control is the best practice. No one solution is best for every species or every situation. When using herbicides, CAKE CISMA is careful to select the product that will be most effective with the least impact on non-target species and systems. We also have a wealth of information on best management practices for invasive species, if you have questions, just ask us!
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