The Spinal Column

Efforts underway to identify and control frog-bit in Oakland County



A small retention pond full of European frog-bit. (Photo courtesy of Oakland County CISMA.)

A small retention pond full of European frog-bit. (Photo courtesy of Oakland County CISMA.)

The Oakland County Cooperative Invasive Species Management Areas (CISMA) have received $205,200 in grants to operate and specifically survey frog-bit, which has been found in Novi and northern Wayne County.

In Novi, frog-bit is present in small retention ponds and wetland areas.

Native to Europe and parts of Africa and Asia, European frog-bit (Hydrocharis morsus-ranae) is a free-floating aquatic plant with small (half-inch to 2.5 inch), heart-shaped leaves that resemble miniature water lilies. Its name is attributed to people observing frogs biting at the leaves of the plant, perhaps to access caterpillars using the leaves for protective enclosures. European frog-bit quickly forms dense colonies in shallow, slow-moving waters. Thick mats can prevent native plant growth, make movement difficult for ducks and large fish, and cause problems for boaters, anglers and swimmers.

European frog-bit was intentionally planted in an Arboretum in Ontario, Canada and escaped cultivation several years later. It has since spread into several of the Great Lakes, although inland locations in Michigan remain rare.

“Frog-bit was discovered in the summer of 2018, and additional surveys in 2019 confirmed more locations,” said Erica Clites, director of Oakland County CISMA. “So far, frog-bit is isolated to nine small retention ponds and wetland areas in Novi, however, without taking appropriate preventative actions it could easily spread through water movement, as well as the movement of ducks to nearby larger lakes. The introduction of frog-bit to large lakes would cause significant impacts for wildlife and people recreating on the lakes. Such an introduction would also increase the spread of the plant, as it can easily be transported on boat motors or trailers, fishing gear and other recreational equipment.”

“Remember that Clean Drain Dry is the law in Michigan, so whenever you recreate on the water, clean your boat or kayak and gear to prevent the spread of frog-bit and other aquatic invasive species,” said Clites.

European frog-bit is difficult to control, and early detection is key to controlling its spread. Management efforts to date include hand pulling of plants or treatment with herbicides.

Central Michigan University is leading a collaboration to understand more about frog-bit plants and their overwintering buds called turions in an effort to identify the most effective control methods. This collaboration incorporates the efforts of CISMAs around the state that are locating and managing frog-bit, as well as the state of Michigan’s Aquatic Invasive Plant Response Team.

The $205,200 grant funding comes from the Michigan Invasive Species Grant Program (MISGP), cooperatively implemented by the Department of Environment, Great Lakes and Energy, the Department of Natural Resources, and the Department of Agriculture & Rural Development. The Oakland County CISMA is managing a collaboration with the Friends of the Rouge, Huron River Watershed Council and the Clinton River Watershed Council to conduct surveys of public and private land in southwestern Oakland County (including Novi, Wixom, Walled Lake, Wolverine Lake, Commerce Township and Milford Township) to locate frog-bit and other watch list species. Grant funds will be used to identify water bodies of interest, create outreach materials, contact private landowners, host public meetings and conduct field surveys. Depending on the results of the surveys, control of European frog-bit may take place at selected locations.

Clites said frog-bit is a prohibited species in Michigan. This means that selling, importing, cultivating or transporting frogbit is not allowed. “Residents of southwestern Oakland County can help control the spread of frog-bit by allowing surveys of ponds and wetlands on their property by our survey team,” she said.

If you see European frog-bit in your area, CISMA asks that you take photos and send them to oaklandcountycisma@gmail.com.

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