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16731 Ferris Street
Grand Haven, MI 49417
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Our Mission is to be your local resource for natural resource management, helping people conserve, maintain and improve our natural resources and environment for future generations in Ottawa County.


Hemlock Woolly Adelgid (HWA) Project Overview

The underside of a hemlock branch

The underside of a hemlock branch.

Characteristic ovisacs

Characteristic ovisacs associated
with hemlock woolly adelgid.

Click Here to Donate
to the Hemlock Woolly Adelgid Project

The Hemlock Woolly Adelgid Crew is working to control and eradicate hemlock woolly adelgid (HWA): an invasive insect that feeds on and kills Eastern hemlock (Tsuga canadensis) trees.

In 2017, the Ottawa Conservation District was a sub-recipient of Environmental Protection Agency funds awarded to the West Michigan Shoreline Regional Development Commission. This money was used to conduct extent surveys and record presence of HWA infestations throughout Lake Michigan's coastal zone. Some of these funds were also used to hire a contractor to begin treatments of HWA. Now, we are building off that work with Michigan Invasive Species Grant Program funds to continue to survey as well as take on treatments of HWA internally. Our team has been working primarily in Oceana County to target the northernmost known HWA infestations. The goal of this work is to cap the northernmost populations to prevent this insect from invading our valuable hemlock resource in the Upper Peninsula. We will continue to move our efforts south as funding allows. Local landowner investment helps us build capacity to take on additional HWA management. Click here to donate to the Hemlock Woolly Adelgid Project.

The effort to slow the spread of HWA and protect stands of hemlock trees will strengthen Michigan's natural forest ecosystem. The loss of the hemlock tree would increase the effects of climate change by allowing the forest temperatures to rise, which would be detrimental to wildlife, as well as the beauty of our natural forests. It would also adversely affect the outdoor recreation economy, especially in northern Michigan.

Hemlock Woolly Adelgid: What is it?

Hemlock woolly adelgids (HWA) are tiny insects native to Japan. Found in the eastern United States in 1951, HWA has since spread to 16 states, from Georgia to Maine, including Michigan. Specifically targeting hemlock trees as their food and reproductive source, HWA sucks moisture and nutrients from a hemlock's needles and shoots. HWA can be found feeding at the base of needles where they attach to woody shoots and are best seen on the underside of a branch.

Measuring 1.5mm in length, HWA is difficult to see but can be identified by finding the white, woolly masses, called "ovisacs." These protective masses, which cover the insects and their eggs, are most detectable in late fall through spring. HWA asexually reproduces and complete two life cycles per year.

How HWA Spreads

HWA can move from tree to tree by coming into contact with:

  • Birds and wildlife
  • Recreational vehicles
  • Equipment and field gear
  • Infested nursery stock

Michigan has over 170 million hemlock trees growing in forests, along streams and riverbanks, and in landscapes throughout the northern lower peninsula and the upper peninsula. Hemlocks are some of the oldest living trees in Michigan, providing important habitat and winter cover for many species.

Signs of Infestation

First, identify any hemlock trees on your property. Hemlocks have:

  • Needles that are flat and are attached individually to the branch, not in bunches like pines
  • Flat needles are roughly a 1/2" long
  • Two white "racing stripes" on the underside of each needle
  • Tolerance to shade

Once you have identified hemlocks on your property, check for these signs of infestation:

  • White, cottony masses about 1/4 the size of cotton swab attached to the twigs, at the base of needles on underside of branches
  • Needle loss and branch die back, no new growth
  • Gray-tinted foliage

Helpful Links

Find a local nature center to help you identify HWA.

Learn how to identify hemlock woolly adelgid (HWA).

Michigan Invasive Species HWA Watch-List.

For more information on how to identify, report, and take action, visit: