Invasive Plants

This recording includes three presentations given during the 2020 Michigan Inland Lakes Convention.

(0:00) Integrating genetics and herbicide studies to improve watermilfoil management outcomes. Ryan A. Thum and Gregory M. Chorak, Montana State University; Jo Latimore, Michigan State University; and Erick Elgin, Michigan State University Extension

Aquatic plant stakeholders in Michigan increasingly recognize that Eurasian watermilfoil (including hybrids with native northern watermilfoil) is genetically diverse, and that strains can differ in their growth, spread, impacts, and herbicide response. A practical challenge for Eurasian watermilfoil management is developing methods that assess genetic variation to predict how a specific watermilfoil population will respond to a proposed control tactic (e.g., a specific herbicide) before implementing management. In this presentation, we illustrate how we are combining genetic survey and monitoring of invasive watermilfoil populations with field and laboratory studies of herbicide response to inform management. One significant finding of our genetic survey of lakes across Michigan is that it is common for a given strain to be found in more than one lake. Identifying lakes that share strains can facilitate communication among stakeholders regarding management experiences on particular strains. Further, by prioritizing strains to target for herbicide studies, quantitative lab and field studies of herbicide response can inform management on multiple lakes containing a given strain. For example, we found one hybrid strain in eight lakes across Michigan, and a laboratory fluridone assay identified this strain as resistant to 6ppb fluridone. Therefore, lakes with a high proportion of this strain of hybrid watermilfoil should not be targeted for control with 6ppb fluridone. In contrast, our fluridone assay identified several strains of watermilfoil that appear susceptible to 6ppb fluridone, and therefore lakes dominated by these strains would likely respond well to fluridone treatment. We will provide updated information on genetic surveys and herbicide studies, and propose next steps for integrating genetic information into management planning and evaluation.

(30:30) European Frog-bit (Hydrocharis morsus-ranae L.): Collaborative efforts towards an adaptive management framework. Blake Cahill, Central Michigan University

European frog-bit (Hydrocharsis morsus-ranae L.; EFB) is an invasive free-floating macrophyte with the potential to reduce the diversity of native plant, fish, and invertebrate communities, alter the physiochemical properties of wetlands, and inhibit the recreational and commercial use of wetlands and water bodies. Since its putative initial escape from cultivation in Ontario in 1939, EFB has been documented in nine U.S. states and two Canadian Provinces. European frog-bit was first documented in Michigan in the Huron-Erie Corridor in 1996 and has since rapidly expanded its distribution in Lake Erie and Lake Huron coastal wetlands. European frog-bit is increasingly being detected in Michigan inland waters and wetlands, including Fletcher Pond in 2013 (Alpena/Montmorency County), Reeds Lake and Fisk lake in 2016 (Kent County), Maybury State Park in 2018 (Oakland County), and Pentwater Lake (Oceana County), Dansville State Game Area (Ingham County), and the Grand River (Ottawa County) in 2019. Monitoring and management efforts have been hampered by information gaps pertaining to biology and ecology, impacts, and effective control strategies, and the lack of a centralized management plan. In spring 2018, a group of stakeholders, including decision makers, regional, state, and local management partners, researchers, and outreach professionals, began meeting to identify critical information and resource needs for EFB management and improve coordination and collaboration among stakeholders. This has resulted in an engaged EFB Collaborative and a collective effort to establish a state-wide species-specific adaptive management framework for EFB management, inclusive of statewide management goals and objectives and short- and long-term strategies for EFB management. We will present on the current state of knowledge on EFB biology and ecology, the achievements of the EFB Collaborative, efforts to address critical information and resource needs, and progress of the first iteration of the EFB adaptive management framework.

(1:00:00) Monitoring and management of starry stonewort (Nitellopsis obtusa) in Wisconsin lakes. Michelle Nault, Wisconsin Department of Natural Resources

Starry stonewort (Nitellopsis obtusa; SSW) was first reported in the U.S. in the 1970’s and has since been documented in portions of the eastern Great Lakes as well as various inland lakes throughout the Midwest. In September 2014, Wisconsin DNR staff discovered a small established population of SSW in a southeastern Wisconsin lake, marking the first time this non-native macroalgae had been reported in the state. Since then, SSW has been verified in over a dozen inland lakes in Wisconsin, as well as coastal portions of Green Bay and northern Lake Michigan. This presentation will highlight the statewide monitoring and management efforts which have occurred after the initial discovery, including an evaluation of management efficacy following the implementation of a variety of techniques (e.g., chemical control, drawdown, hand-removal, DASH, etc.) to control this new invader.