Capitol News

Most people do not often consider the risks associated with firewood, but Michigan’s Invasive Species Program is using Firewood Month to highlight how moving firewood can spread invasive pests and diseases that threaten the state’s forests.

Insects such as the emerald ash borer and fungi like oak wilt are among the threats that can kill healthy trees. Once a tree dies or becomes weakened—whether by pests, disease, drought, or storm damage—it may harbor insects and fungi that survive in the wood even after it has been cut. This means firewood can transport harmful organisms to new locations.

“Wood borer” refers to beetles that lay eggs on or under tree bark. Their larvae tunnel into wood, damaging tissues essential for water and sap movement. While many borers are native and target weakened trees, invasive species like emerald ash borer and Asian longhorned beetle attack healthy ones as well. A Michigan study found that 23% of 1,045 pieces of transported firewood contained live borers; another 41% showed signs of previous infestation.

Adelgids are small insects feeding on conifers such as pines and firs. Efforts are underway in west Michigan to control hemlock woolly adelgid, while balsam woolly adelgid is being managed in Clare, Missaukee, and Oceana counties by the Michigan Department of Agriculture and Rural Development. Adelgids are hard to see but can be identified by white tufts they produce for their eggs. Over time, these pests can kill host trees by depleting sap.

Fungal diseases also pose a risk to forests. Both native and invasive fungi move via spores or other structures—sometimes spread by beetles—and remain alive in dead wood. Transporting infected firewood can spread diseases such as oak wilt or Dutch elm disease far beyond their natural range.

Spongy moths (formerly known as gypsy moths) present another problem; while females cannot fly, they deposit egg masses on vehicles, equipment, and firewood that people then move around the state. The recently detected spotted lanternfly could spread similarly unless precautions are taken.

The program emphasizes: “Wood that looks clean and healthy can harbor tiny insects, eggs or microscopic fungi spores that can start a new and deadly infestation. Always leave your backyard firewood at home, even if you think it looks fine.”

To prevent spreading pests:

- Do not move aged or seasoned wood—even dry wood may still contain insects.

- Buy firewood close to where you will burn it; use only local wood (within 50 miles).

- Certified heat-treated firewood is safe for long-distance transport; look for federal certification marks.

- Do not take unused purchased firewood home from campsites.

- Inform others about safe practices regarding moving firewood.

More than half of Michigan is forested with an estimated 14 billion trees statewide. Forests contribute significantly to landscapes across parks, river corridors, sidewalks, and neighborhoods throughout Michigan.

“Making safe firewood choices helps to protect the diversity and health of Michigan’s forest resources,” according to information from the Invasive Species Program.

Michigan's Invasive Species Program is jointly managed by the Department of Environment, Great Lakes, and Energy; Department of Natural Resources; and Department of Agriculture and Rural Development.

Further information about protecting trees from invasive species is available at DontMoveFirewood.org.