Species that are not native and also have the potential to harm human health or to harm natural, agricultural or silvicultural resources can be listed as prohibited or restricted by the State of Michigan. If a species is prohibited or restricted, it is unlawful to possess, introduce, import, sell or offer that species for sale as a live organism, except under certain circumstances.
- 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.
- 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.
- 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.