Invasive species update: hemlock woolly adelgid

Hemlock woolly adelgid, an invasive insect that can kill Eastern hemlock trees, has infested areas of Allegan, Ottawa, Muskegon and Oceana counties.

A native of Asia, the hemlock woolly adelgid (HWA) probably arrived in the eastern U.S. on a shipment of hemlock from Japan. It was first identified in Richmond, Virginia in 1951 and by the 1980s had spread to large tracts of forest in the Appalachian Mountains. In 2001, an external quarantine restricted the shipment of hemlock to Michigan from states infested with the adelgid. Isolated populations of HWA were discovered in Michigan beginning in 2006. Though these populations were successfully eradicated by 2015, new infestations were found in Ottawa and Muskegon counties in that same year. Infestations were found in Allegan and Oceana counties in 2017. Both private and public lands are affected, including seven state parks within these four counties.  View a map of known infestations in Michigan at Michigan.gov/HWA.

The problem:

Hemlock woolly adelgids suck sap out of hemlock trees. Their feeding can kill needles, shoots and branches. Over time, tree growth slows, and trees may take on a grayish-green appearance. Without treatment, infested trees can die within four to 10 years.

Most of Michigan’s 170 million hemlocks are found in forests, dunes and river corridors, mainly along the Lake Michigan shoreline and in the northern lower and upper peninsulas. Hemlocks also are found in residential areas, parks and developed areas throughout the state. Loss of hemlocks would have a significant impact on natural and developed areas in Michigan. Hemlocks provide shelter for deer and nesting birds and keep forest streams – including designated trout streams – cool and clean. Weakened trees on a home or park landscape can become hazards and may have to be removed. HWA can be moved to new locations on birds, mammals, infested hemlock nursery trees, logs and/or firewood. The insects also can be moved by humans if clothing, vehicles or gear come in contact with an infested tree.

Management:

The Hemlock Woolly Adelgid Coordinating Committee provides direction for survey, management and outreach efforts. It includes representatives from the Michigan departments of Natural Resources and Agriculture and Rural Development, Michigan State University, the U.S. Department of Agriculture’s Forest Service and the Ottawa County Parks and Recreation Department.

Because certain insecticides are effective in treating trees with HWA, it is possible to save hemlocks that have been infested. Currently, management efforts are focused on identifying all existing HWA populations and assuring they are treated in order to contain the infestation. Management also involves outreach to enlist the public’s help in identifying and reporting new HWA locations and preventing the spread of HWA by people and their activities. Response efforts in Allegan, Ottawa, Muskegon and Oceana counties include surveys of hemlock forests on public and private lands and treatment of infested trees in these areas.  Additionally, surveys are underway in Lake Michigan lakeshore counties from Berrien to Emmet in the Lower Peninsula and from Mackinac to Menominee in the Upper Peninsula. Statewide management efforts are being undertaken by the Michigan departments of Natural Resources and Agriculture and Rural Development, along with Cooperative Invasive Species Management Areas (CISMAs) which are groups of non-profit and government agencies, businesses and volunteers working together to tackle invasive species in their regions.

Quarantine:

Along with the 2001 external quarantine, MDARD issued an internal quarantine in 2017, restricting the movement of hemlock nursery stock and unprocessed hemlock products from or within Allegan, Muskegon, Ottawa and Oceana counties. To date, no infestations have been found outside of this core area.

Public outreach:

Public support is vital. Identifying and reporting populations of hemlock woolly adelgid helps prevent its spread. State agencies and partners are engaged in education and outreach efforts across the state.

Key messages for the public:

• Hemlock woolly adelgid, an invasive tree pest, is infesting Eastern hemlock trees in west Michigan.
• Learn how to identify hemlock trees and hemlock woolly adelgid.
• Check your hemlock trees from late fall to early spring for signs of hemlock woolly adelgid.
• Know how to report hemlock woolly adelgid if you find it.
• Prevent the spread of hemlock woolly adelgid. Do not move hemlock trees, branches or firewood within or out of the quarantine area.

Finding and reporting HWA:

     Identify hemlocks

Since HWA feeds and reproduces only on hemlock trees in Michigan, it is important to distinguish hemlocks from other conifers like pines or spruces. Look for: Pyramid-shaped trees up to 75 feet tall. Drooping or feathery branches. Short (1/2 inch), flat needles growing individually from the sides of twigs. Needles that are dark green on top with two parallel, white stripes underneath. Papery cones about three-quarters of an inch long hanging downward from branches.

     Look for HWA

Late fall through early spring is the best time to check hemlock. Look on the undersides of branches for evidence of round, white ovisacs near the base of the needles. Up close, ovisacs look like balls of spun cotton and may appear alone or in clusters. The short video Hemlock woolly adelgid: invasive species in Michigan provides helpful identification tips. Other, less damaging pests easily can be mistaken for hemlock woolly adelgid. Be sure to review photos and descriptions of common hemlock woolly adelgid look-alikes at www.michigan.gov/HWA.

My name is Drew Rayner and I work for the Michigan DNR, specifically working on hemlock woolly adelgid (HWA). If you have not heard of HWA, it is a forest pest that is attacking our hemlock trees here in Michigan and if left unaddressed, will lead to tree mortality. I am reaching out because your township is in an area that is known to have HWA and I would like to be a resource to the Township and its residents. My position allows me to speak at meetings and outreach events, conduct trainings on how to properly treat trees for this pest, and be a resource to confirm the presence/absence of this species and provide advice. I would be more than willing to speak with anyone on this issue and provide more information so I can figure out how to be a better resource for you all. Please feel free to share my contact information with any residents that have questions or let me know if the township has any needs that I can assist with.

Thank you,
Drew

Drew Rayner

West Michigan HWA Coordinator

Michigan Department of Natural Resources

517-231-8763