The team for the first Ginger Creek treatment in April 2025, with Hydrilla Task Force members from the Illinois Department of Natural Resources, Forest Preserve District of DuPage County, Lake County Health Department, DuPage River Salt Creek Workgroup and SePRO. All photos courtesy of the author.
The Aquatic Nuisance Species Program in the Illinois Department of Natural Resources (IDNR) Division of Fisheries is at the forefront of combatting invasive aquatic organisms in Illinois. Staff in this program devote their days tackling threats to Illinois waterways, but with a footprint that covers the entire state, they aren’t able to find everything. That why we rely on members of the public to not only do their part to prevent the spread of aquatic nuisance species by recreating responsibly and never releasing aquatic life into the wild, but also to be our eyes and ears. Be a Hero and Transport Zero and report suspected invasive species. This role is especially important for new invasive species that are not established in Illinois.
Public reporting played a key role recently in detecting a major threat to Illinois waterways. In the fall of 2024, members of the Ginger Creek Homeowner’s Association in Oak Brook contacted the Aquatic Nuisance Species Program. They reported that hydrilla had been detected in their lake by a private contractor conducting a routine lake survey. The infestation was reported to cover approximately 40 percent of the 26-acre lake and had likely been growing undetected for some time. IDNR staff confirmed the identity of the plant and recognized the magnitude of the threat.
Hydrilla (Hydrilla verticillata) is considered the perfect aquatic weed. It can grow rapidly, up to an inch a day, survive in a wide variety of aquatic habitats, and spread through a variety of mechanisms, including fragmentation and tubers. Fragmentation means a small part of the plant can break off, float downstream and establish a new population. Tubers are small potato-like storage structures that can survive in aquatic sediments for more than seven years before sprouting. This ability to spread quickly and persist long-term even in treated systems means that hydrilla infestations often require years of management to fully eradicate and can have major ecological, economic and recreation impacts. These impacts include outcompeting native plants and creating dense patches that impede boat navigation.
After introductions from Asia to the United States in the 1950s and 1970s, hydrilla was first detected in the Great Lakes Basin in 2002, and has since been detected in New York, Ohio, Pennsylvania, Michigan, Indiana, Wisconsin and Illinois. The U.S. Department of Agriculture estimates that 52 to 94 percent of the United States is suitable for the establishment of hydrilla. States in the eastern and southeastern United States where hydrilla is prevalent spend millions of dollars annually on hydrilla management. The U.S. Army Corps of Engineers estimates the financial loss associated with hydrilla establishment in the Great Lakes alone to be between $70 and 500 million annually when looking at impacts to fishing, swimming, boating and navigation. Therefore, any new detections of hydrilla are treated with the utmost urgency, as the biological and financial costs associated with long-term management far exceed the costs associated with the development of prevention programs and early eradication efforts to prevent establishment.
Illinois has long recognized the extreme danger posed by hydrilla, and in 2014, detections in nearby states prompted the formation of the Hydrilla Task Force, an interdisciplinary technical advisory group comprised of members from state, county, municipal, regional, university and private organizations. The mission of the group is to minimize the adverse impacts of hydrilla on aquatic ecosystems throughout the state of Illinois by sharing expertise, equipment, materials, staff, and volunteer labor to control, manage, and eradicate confirmed hydrilla infestations in the state of Illinois.
Illinois has been lucky to remain largely free of hydrilla. In fact, the detection in 2024 was only the second instance of hydrilla reported in the state. The first was in 2019, when hydrilla was detected in northeastern Illinois in a 3-acre detention basin in Lake County less than 6 miles from Lake Michigan. In both cases, quick, decisive action by the Hydrilla Task Force helped keep these invasions at bay. The Hydrilla Task Force was mobilized successfully in 2019 to eradicate the infestation in Lake County and was reactivated in 2024 to combat the infestation in DuPage County.
Performing rapid field assessments in fall 2024, the Hydrilla Task Force surveyed the entirety of the Ginger Creek system downstream of Ginger Creek Lake, covering approximately 70 acres. These rapid assessments indicated that hydrilla is also established in the country club immediately downstream of the initial site. No rooted hydrilla was found downstream of this secondary location; however, hydrilla fragments were found up to 0.8 miles downstream from the rooted plants. There is approximately one mile between the most downstream-detected hydrilla fragments and the mouth of Ginger Creek where it empties into Salt Creek, a major tributary of the Des Plaines River.
To keep hydrilla from spreading outside of Ginger Creek to other major waterways in northeastern Illinois, the Hydrilla Task Force developed a comprehensive treatment and monitoring plan, which was implemented in 2025. A key part of this process included coordinating closely with local landowners, as the entire creek system is privately owned and permission was needed for property access and product application. Community engagement efforts included the distribution of outreach materials to educate on hydrilla identification, and issuing a press release to notify the public to be on the lookout for additional populations of hydrilla.
Treatment of the system began in April 2025. Low-dose aquatic herbicide treatments were applied monthly from April to September 2025. Treatment was conducted throughout the entire 70 acres of the Ginger Creek system, including in downstream areas where hydrilla had not been detected. These protective downstream treatments were conducted in case there was lingering hydrilla that had not been detected during the previous fall’s rapid assessments, and to create an environment inhospitable to hydrilla in the event that any fragments from the initial site floated downstream. Applying herbicide at low concentrations ensured that there would be no impact to irrigation, recreation or wildlife, which was critical to get landowner approval for the treatments.
Monitoring plans for the creek system include annual vegetation monitoring to determine treatment efficacy and guide future planning. Comprehensive vegetation surveys conducted across 330 sites in September 2025 by the Hydrilla Task Force revealed no hydrilla present, an encouraging result. Due to the ability of hydrilla to persist long-term in systems, continued monitoring and treatment will be conducted for multiple years.
Communication and partnerships have been key to a successful endeavor. Partners within the Hydrilla Task Force have been generous with their time and expertise, with key financial support provided by the DuPage River Salt Creek Workgroup, a non-profit partner, to cover gaps in funding. Landowners have been cooperative and communicative throughout the process and are dedicated to ensuring that hydrilla does not spread beyond their properties. Without quick communication from local landowners, the hydrilla infestation could have quickly spread out of control with major impacts on waterways in Illinoi
IDNR and the Hydrilla Task Force remain committed to ensuring that hydrilla does not become a permanent presence in Illinois and to reminding the public to do their part to prevent the spread of aquatic nuisance species. The suspected source of the current invasion and the initial invasion in 2019 were illegal releases from aquaria or water gardens. Hydrilla is listed both as an Illinois Injurious Species and a Federal Noxious Weed, meaning that it is illegal to purchase, possess or transport the plant within Illinois and in the U.S.
It is up to every individual to make sure they are doing their part to help prevent the spread of aquatic nuisance species. Keep up-to-date on natural resources regulations, be aware of what species are prohibited, and never release aquatic life. Review the Be a Hero Transport Zero website to learn more about aquatic nuisance species and how you can take action. When in doubt, or if you think you have detected an invasive species, take photos and submit them to DNR.ANS@illinois.gov with any concerns. A quick message can make a big difference in timelines and resources, and our waterways will thank you!
Claire Snyder is a Natural Resources Specialist with the Illinois Department of Natural Resources. She works within the Aquaculture and Aquatic Nuisance Species program, primarily providing support to the Aquaculture Program manager, overseeing aquatic life transport, aquaculture facilities and aquatic nuisance species concerns across the state. She has been with the department since 2020. She obtained her Master’s of Science in Zoology from Southern Illinois University.
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