Hydrilla Herbicide Treatment in Eno River to Begin May 27

  • 21 May 2015
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Hydrilla Herbicide Treatment in Eno River to Begin May 27
Hydrilla is a highly destructive, nonnative aquatic plant from Asia that creates nearly impenetrable mats of stems and leaves of the surface of lakes, rivers and other waterways.

DURHAM, N.C. (May 21, 2015) — To combat a rapidly spreading hydrilla infestation in the Eno River, the Eno River Hydrilla Management Task Force has approved a plan to apply an EPA-approved herbicide in the river from Lawrence Road to N.C. Highway 501, located in Durham and Orange counties.

The task force has hired SePRO Corporation based in Carmel, Ind., with research and support facilities in Whitakers and Rocky Mount. SePRO will apply the herbicide, Sonar Genesis® (fluridone), in a 16-mile target zone of the river, starting May 27, weather permitting, through the end of September.  The company will apply the herbicide in a concentration well within the limits approved by the EPA— a concentration that is both safe for swimmers and boaters and non-toxic to fish and wildlife.

The herbicide treatment project is part of a two-year pilot program to reduce the presence of hydrilla in the Eno River. Hydrilla is a highly destructive, nonnative aquatic plant from Asia that creates nearly impenetrable mats of stems and leaves of the surface of lakes, rivers and other waterways. It crowds out native vegetation, reduces recreational opportunities, and ultimately can harm fish and other aquatic organisms, as well as bird species. The plant also can clog intakes in rivers and reservoirs that are used for drinking water supplies and irrigation.

While task force members don’t expect any significant injury to non-target plants within or adjacent to the treatment areas, they recommend that homeowners with properties adjacent to the river not use treated water for irrigation without consulting a task force member first.

“Although little or no irrigation use is known within the management zone, we will contact individuals with properties adjacent to the parts of the river being treated with specific restrictions and precautions regarding irrigation use,” said Rob Emens, aquatic weed control specialist with the N.C. Division of Water Resources.

The application of fluridone in the Eno River will be the first time the herbicide has been used in a river in North Carolina to combat hydrilla, although it has been used successfully for many years in Lake Gaston, Lake Tillery, Tar River Reservoir and Lake Waccamaw to control hydrilla.

Hydrilla was first discovered in the Eno River basin in the early 1990s in Lake Orange, which is located upstream of Hillsborough. In 2009, biologists confirmed hydrilla in another upstream reservoir, West Fork Eno Reservoir. The N.C. Division of Water Resources is actively managing hydrilla in both upstream reservoirs. 

Members of the task force conducted a survey in fall 2013 and detected hydrilla at different densities in 25 miles of the river. The most infested area was about 15 miles of river from the N.C. Highway 70 Bridge in Hillsborough to Guess Road in Durham.

“Hydrilla has significantly affected recreational opportunities in the Eno River,” said Mark Fowlkes, the Piedmont aquatic habitat coordinator with the N.C. Wildlife Resources Commission. “Specifically, when hydrilla has reached its full growth for the year, it is almost impossible to fish, kayak or wade in the river.”

Because hydrilla grows so quickly and can form new plants from tiny fragments, it could get established in Falls Lake and become a serious nuisance in terms of recreation and water supply.

“After extensive research, the task force decided that fluridone is the best option to manage hydrilla in the treatment area,” Fowlkes said. “We considered other herbicides, but fluridone was the safest one for human health and non-target native plants and animals.”

In addition to evaluating multiple herbicidal treatment options, task force members considered other alternatives, such as physical removal on a small scale, which had a poor outcome. The task force also considered using sterile grass carp, a biological control that is not appropriate for the Eno River because the fish feeds indiscriminately not only on the targeted non-native hydrilla, but also on native aquatic plants important to the Eno’s fish and wildlife communities.

The task force outlined its herbicide pilot project at a public meeting held on April 29 in Hillsborough. More than 20 people attended the open-house style meeting where experts described the threat hydrilla poses in the Eno River basin, provided information on the project and addressed questions from the public.

The Eno River Hydrilla Management Task Force comprises a group of federal, state and local government representatives, including the N.C. Wildlife Resources Commission, N.C. Division of Water Resources, and N.C. State Parks, which has been working since 2007 to evaluate and address the hydrilla threat in the Eno River.

For more information on the pilot project, visit http://nc-ipc.weebly.com/eno-river-hydrilla-project.html or contact Emens at rob.emens@ncdenr.gov or 919-707-9012.

a high-resolution version of the photo above. Please credit Erik Nygard;
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