State’s watch list recently updated
Michigan’s invasive species watch list was recently updated to include two new species and remove another. Mountain pine beetle, a deadly threat to pine trees, and water-primrose, a fast-spreading aquatic plant, have been added to the watch list due to threats they pose to native ecosystems and industry. European frog-bit, originally listed in 2011, has been moved off the list of species of immediate concern and is now considered established in the state.
Mountain pine beetle
Mountain pine beetle has been characterized as the most aggressive, persistent and destructive bark beetle in the western U.S. and Canada. Hot, dry summers and mild winters in these areas have led to the beetle’s unprecedented population growth and range expansion, moving it ever closer to Michigan.
Because it attacks most species of pine, the invasive beetle could have widespread effects in the state.
“White and red pines are primary species in our forest ecosystems, and jack pine serves as critical habitat for the Kirtand’s warbler,” said Susie Iott, invasive species program specialist with the Michigan Department of Agriculture and Rural Development. “If mountain pine beetle were to become widely established in Michigan, it would cause severe losses across multiple industries, including timber products, plant nurseries and tourism.”
Because the beetle can be transported on infested pine logs, firewood and other similar commodities, MDARD issued an exterior mountain pine beetle quarantine in 2020 to regulate the movement of all firewood and any pine products with bark attached from areas of the western U.S. and Canada.
Water-primrose (Ludwigia species) is a group of very similar non-native plants, L. grandifolia, L. peploides and L. hexapetala, that are invasive in wetland ecosystems. Water-primrose is quick to establish and spread in dense mats within wetlands and shoreline areas, outcompeting native species and making boating and water access difficult.
Three known populations, two in the greater Detroit area and one in Ottawa County, indicate the species can survive and thrive in Michigan’s climate. Once established, water-primrose can be very difficult to remove, making early detection critical.
“Water-primrose is not a regulated species in Michigan. Though not common in trade, it was likely introduced through the landscape or water garden pathway,” said Bill Keiper, aquatic biologist with the Department of Environment, Great Lakes, and Energy. “Several Ludwigia species are common in trade but are not invasive and look much different than water-primrose.”
A recent review of European frog-bit, an invasive aquatic plant, determined that the plant no longer met watch list criteria due to its establishment in many areas of the state. European frog-bit still retains its prohibited status, making it unlawful to possess, introduce, import or sell in Michigan. State and local management efforts for European frog-bit will continue despite the status change.
Michigan’s Invasive Species Program continues to participate in the European Frog-bit Collaborative, which aims to improve coordination among stakeholders, establish communication networks and build consensus on next steps for management and research. Significant investments continue to support efforts, largely led by local conservation groups, to reduce the invasive plant’s spread.