Great Lakes Hydrilla Collaborative

Case Studies

A series of case studies will be provided here for stakeholder review. These case studies provide examples of the implementation of management and monitoring techniques in a variety of systems within and adjacent to the Great Lakes Basin, in the hopes that there are lessons learned that you can apply to your own projects.


Boat in Tonawanda Creek

Tonawanda Creek/Erie Canal Hydrilla Eradication Project, New York

This project is a multi-year field-scale demonstration project to manage monoecious hydrilla in a flowing water system in Western New York. Management activities began in 2014 and have focused on chemical treatment of hydrilla infestations within a 15-mile-long stretch of creek/canal. Control efforts have progressed over time, and treatment is now focused on testing different methods of effectively treating isolated patches of hydrilla within the creek/canal.

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Hydrilla in West Creek Reservation
Hydrilla in West Creek Reservation, 2010; courtesy of Jennifer Hillmer

Cleveland Metroparks, Ohio

Hydrilla was first identified in the Cleveland Metroparks in 2011 at three separate locations, followed by additional detections in 2012 and 2013 in a total of six inland waterbodies (four of which are man-made ponds or wetlands). Metroparks has managed the hydrilla infestations primarily through an evolving herbicide treatment plan, supplemented with water draw-downs, barriers, and filters. In addition to the following project documents, their current webpage provides published annual hydrilla reports and images of signage used.

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Monitoring efforts
Monitoring efforts; photo courtesy of Racine-Johnson Aquatic Ecologists.

Cayuga Lake Inlet, Fall Creek, and Southern Cayuga Lake, Ithaca, New York

Monoecious hydrilla was first found in the Cayuga Inlet in 2011. The inlet is a tributary to Cayuga Lake, located in the Finger Lakes Region of New York. Following the discovery of the infestation, the Hydrilla Task Force of the Cayuga Lake Watershed was formed, composed of four working groups. Treatment in the inlet occurred annually between 2011 and 2016, with a combination of a contact herbicide and fluridone. No hydrilla has been found in the inlet since 2015. In 2013, Hydrilla was discovered in Fall Creek, a tributary of Cayuga Lake, and in the southeastern portion of Cayuga Lake. Annual treatments in Fall Creek ended after 2017 and included a combination of endothall and fluridone, and treatments in southeastern Cayuga Lake, a high exchange environment, have included a combination of chemical and physical methods. No hydrilla was found in Fall Creek in 2017, and increased monitoring efforts will replace herbicide applications in 2018. Several selected documents are included below, but for more information, please visit the following website: http://ccetompkins.org/environment/invasive-nuisance-species/aquatic-invasives/hydrilla/fighting-hydrilla-in-the-cayuga-lake-watershed.

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Herbicide application in Wells College Bay
Herbicide application in Wells College Bay; photo courtesy of Ecology and Envrionment

Wells College Bay / Village of Aurora, Cayuga Lake, New York

This project is a multi-year field-scale demonstration project to manage monoecious hydrilla in a high water exchange environment within Cayuga Lake. Management activities began in 2017 and focused on chemical treatment of hydrilla infestations within a 59-acre area.

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Lake Manitou hydrilla sightings
Lake Manitou hydrilla sightings 2006-2016, courtesy of SePRO, Aquatic Control, Aquatic Weed COntrol, and ReMetrix

Lake Manitou, Indiana

The Indiana Department of Natural Resources (IDNR) discovered monoecious hydrilla Lake Manitou, an 809-acre lake in Fulton County, in the summer of 2006. Between 2006 and 2016, hydrilla was managed with whole-lake and partial lake herbicide treatments. Treatments evolved with advances in herbicides and application methodologies, as well as monitoring results. Hydrilla was not detected in 2016 lake surveys and was again not detected in any of the 2017 lake surveys, and it is projected that the IDNR’s management efforts have successfully eradicated hydrilla from Lake Manitou.

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Deep half of the pond following dewatering in fall 2007
Deep half of the pond following dewatering in fall 2007; photo courtesy of Wisconsin Department of Natural Resources

Response to the First Verified Discovery of Hydrilla in Wisconsin

Hydrilla was first found in an excavated private pond in Marinette County, Wisconsin in 2005, and was verified as monoecious hydrilla in 2007. A team that included federal, state, and local agencies developed a response plan to guide management activities. The plan outlined chemical treatment (August 2007 and June 2008), dewatering the pond to freeze hydrilla tubers and propagules (October 2007), and excavation of the sediment for tubers (November 2007). Intensive monitoring following chemical treatment in 2008, and during 2009 and 2011 indicated no visible signs of hydrilla growth. Periodic monitoring conducted since 2011 has also not detected any signs of hydrilla growth, and this population is believed to have been eradicated at this location.

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