MADISON, Wis. – The Wisconsin Department of Natural Resources is launching a project to eliminate localized populations of an aquatic invasive species commonly known as tall mannagrass and is seeking help from property owners to map the invader’s whereabouts.
A summer photograph of tall mannagrass (Glyceria maxima) in front of cattails. Note the widely spread seed head and light green color.
Photo Credit: DNR
The reed, formally known as Glyceria maxima, is constrained to very wet conditions and tends to be found in marshes, streams and drainage ditches, said Jason Granberg, DNR water resources management specialist. Elsewhere, the plant has posed a threat to dairy and beef cattle because consumption of its young shoots may sicken or kill animals. It also makes water stagnant and unpalatable for animals to drink.
Native to Europe, Glyceria maxima forms thick stands that crowd out native plants and impair habitat for fish. The plants also slow stream flow, reduce dissolved oxygen, increase siltation and can create a potential flooding hazard in low lying areas next to streams.
Granberg said the aquatic invader has limited distribution within the United States, with a documented presence in Massachusetts, Connecticut, Wisconsin, Minnesota and the state of Washington. Wisconsin DNR is asking for help from property owners in Dane, Jefferson, Waukesha, Milwaukee, Racine, Kenosha, Ozaukee, Washington, Dodge, Door, Calumet, Winnebago, Wood and Oneida counties so that the department can find populations, map the extent of its spread and plan chemical treatments.
A thick matt of Glyceria maxima, shown in winter conditions, is impeding the flow of water in this stream and reducing fish habitat.
Photo Credit: DNR
“We’d like to hear from homeowners who think they may have tall mannagrass on their properties so that we can offer an herbicide treatment,” Granberg said. “We have funding to provide free treatment for control of this plant. Also, we will be testing the effectiveness of glyphosate and imazapyr on controlling this species. Both of these treatments are commonly used herbicides for agricultural and home garden applications and have U.S. Environmental Protection Agency approval.”
The herbicide application will only occur on properties where DNR has received written consent from the landowners and where all adjacent landowners have been informed of the project. The herbicide application will be paid for using a grant from the Great Lakes Restoration Initiative. Prior to treatment, DNR is making an environmental analysis available for public review and comment.
To view the environmental analysis, visit DNR.wi.gov and search http://dnr.wi.gov/topic/invasives/fact/pdfs/GlyceriaMaximaControlEA07012016.pdf. Comments should be emailed to Jason.Granberg@Wisconsin.Gov or mailed to Jason Granberg, DNR Water Quality, 101 S. Webster St. Madison, WI 53703, Room WT/3 by Aug. 5, 2016. Questions related to the project also may be directed to Granberg at 607-267-9868 or Jason.Granberg@Wisconsin.Gov.
More information and pictures about Glyceria maxima may be found on the DNR website by searching for “tall manna grass.” By late July, the plant will have well developed seed heads and can be readily seen in wetlands or in saturated soils. This plant is not found in dry uplands.
Landowners who suspect they have the plant on their properties may contact Granberg for identification assistance. Digital photographs from the property owner and location details are greatly appreciated and may be emailed to Jason.Granberg@Wisconsin.Gov.