Protecting the health of Michigan's forests is a challenging task that requires collaboration. Our forest health professionals work with other state and federal agencies and universities to prevent, evaluate and manage the occurrence and impacts of both native and exotic forest insects and diseases.
- 2020 Forest Health Highlights Report
- View and report Heterobasidion root disease locations
- View and report oak wilt locations
Species of concern
- Asian Longhorned Beetle
Watch List - Prohibited in Michigan
The Asian longhorned beetle can attack and kill many tree species including poplar, willow, sycamore, and horse chestnut, but its favorite host are maple trees. The larvae feed in tunnels in the wood of the tree branches and trunks, eventually killing the tree.
- Beech Bark Disease
(Cryptococcus fagisuga + Neonectria spp.)
Beech bark disease (BBD) is caused by both a sap-feeding scale insect and a fungus. American beech trees are first infested with beech scale. Scale feeding allows infection by the Neonectria fungus. The fungus kills the wood by blocking the flow of sap. Some infected trees break off in heavy winds before dying. The scales are covered with white wool, turning infested portions of the tree white.
- Emerald Ash Borer
Prohibited in Michigan
The Emerald Ash Borer is a bright, metallic green insect with purple abdominal segments under its wing covers. They are approximately 1/2 inch in length and can fit on the head of a penny. The larva are worm-like. The adults feed on the foliage of ash tress and the larvae tunnel and feed on the underside of the bark.
- Hemlock Woolly Adelgid
*Detected in Michigan*
These tiny insects secrete white wax as they feed on sap from hemlock shoots and branches. Hemlock woolly adelgid (HWA) feeding can kill needles, shoots and branches, resulting in tree death.
- Oak Wilt
Oak wilt kills healthy red oaks. White oaks can also be affected but are more resistant and less vulnerable to mortality from the disease. Look for red oaks that suddenly drop their leaves in the summer. The disease spreads, killing nearby oaks from one year to the next.
- Spotted Lanternfly
The spotted lanternfly sucks sap from the stems and leaves of orchard trees, grape vines, oaks, pines and other host plants. Feeding can weaken the plant and eventually contribute to its death. Trees will develop weeping wounds that attract other insects and excreted fluids from spotted lanternflies can cause mold growth on plants.
- Thousand Cankers Disease
(Pityophthorus juglandis + Geosmithia morbida)
Thousand Cankers Disease involves an insect native to the southwestern U.S. The disease affects black walnut trees, a valuable economic and ecological resource in Michigan.
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