Reed manna grass (Glyceria maxima) is an aggressive invasive plant species that ecologists historically don’t know much about. But that’s changing as ecologist Heather Patti of R.A. Smith National and wetland ecologist Alice Thompson of Thompson & Associates are embarking on the second year of a two-year field study of this uncommon invasive species.
Reed manna grass began its spread into Racine County, Wisconsin, and more specifically, the Village of Mt. Pleasant in the mid-1970s. The study area is located along the Pike River corridor and encompasses several hundred feet of a 30-acre segment of a 450-acre environmental corridor, Village-owned park that includes restored waterway, wetlands and prairie. There is a concern that this invasive species could spread downstream where future restoration is being planned on what is one of the largest river restoration projects in the upper Midwest. Planning of this restoration project has been ongoing for more than a decade, and is focused on protecting and improving critical fish, wildlife and waterfowl habitat.
Unlike most invasive species which spread in a northerly direction, reed manna grass has reportedly travelled south from the Canadian region into the Lower 48. In the U.S., the species has been identified in both Massachusetts and Wisconsin. Its origin is temperate regions of Europe and Asia, and is well established in portions of Canada, New Zealand, Australia and South Africa (Wei and Chow-Fraser, 2006; Kortze, 2006).
What may be most alarming about reed manna grass is that it can outcompete both invasive and native species, such as cattails, threatening wetland function and diversity. Reed manna grass can form dense, impenetrable stands over large areas and along riparian corridors. It is listed as both a prohibited and a restricted species under Chapter NR 40, an invasive species rule by the Wisconsin Department of Natural Resources.
Having first observed the invasion of this species just two miles from her home in Racine, Wisconsin, R.A. Smith National’s Heather Patti recently got the opportunity to partner with Alice Thompson of Thompson & Associates Wetland Services and the Village of Mt. Pleasant to complete a unique, two-year control study on this species. The study was made possible through a 75% matching grant from the Wisconsin Department of Natural Resources’ Aquatic Invasive Species Control Grants Program.
Heather and Alice began their study in 2011 after having observed this species for several years. As part of the study, two herbicides are being used to treat and control this species and the effects are being monitored and documented. The study involves three replications of Aquaneat® & Habitat® herbicide treatments with a split plot design. Using this method, three distinct areas are individually treated with each herbicide during two different times of the year to compare the results of each. To date, successful die-off has been observed using both herbicides, but some re-sprouting will likely occur in some plots. The Habitat® herbicide caused a heavier die-off of the Glyceria, and impacted several native species growing in the plots. The study is continuing in 2012 with plans for additional treatments and monitoring.
The Village of Mt. Pleasant has been very pleased with the study results. Bill Sasse, director of engineering, Village of Mt. Pleasant, said, "Heather Patti and Alice Thompson have a long history of aiding the Village in the plant management of the Pike River corridor, and we are very happy that they were funded to study the Glyceria maxima that is located there. Their work adds the component of providing a research environment to the beneficial uses of the corridor and aids the Village in controlling invasive species in the area."
Heather and Alice recently presented a poster depicting their 2012 study results at the Wisconsin Wetlands Association Conference in Lake Geneva. They are looking forward to presenting the final results of their study and sharing their insight with state and local government agencies and environmental preservation groups at the 2013 Wisconsin Wetlands Conference.
For more information about this study, or other invasive species questions, contact Heather Patti, PWS, at R.A. Smith National, 262-317-3361.