Second Year of Hydrilla Management Pilot Study in Eno River Begins First Week of May

  • 29 April 2016
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Second Year of Hydrilla Management Pilot Study in Eno River Begins First Week of May
Hydrilla in the Eno River in September 2014

DURHAM, N.C. (April 29, 2016) — The second year of a two-year pilot project to treat parts of Eno River for a hydrilla infestation will get underway the first week of May and last through September.

The Eno River Hydrilla Management Task Force once again has hired SePRO Corporation to apply the herbicide Sonar Genesis® in a 16-mile target zone of the river from Lawrence Road to N.C. Hwy. 501 (Roxboro Road) in Orange and Durham counties. 

SePRO will apply the herbicide in a concentration well below the limits approved by the U.S. EPA (Environmental Protection Agency) — a concentration that is both safe for swimmers and boaters and non-toxic to fish and wildlife.

The task force contracted with SePRO to perform the initial application last year, which was the first time the herbicide had been used in a North Carolina river to combat hydrilla. Initial results indicate that the first application worked well, and task force members hope this second year will bring even greater results. SePRO is based in Carmel, Ind., with research and manufacturing facilities in eastern North Carolina.

“The first year of treatment showed a high degree of success, with a significant lowering of the amount of hydrilla in the treatment area as compared with areas of the river that were not treated,” said Eno River State Park Superintendent Keith Nealson. “We are hoping in this second year to add on to that success.”

Hydrilla is a highly invasive, nonnative aquatic plant that originated in Asia and creates nearly impenetrable mats of stems and leaves on the surface of lakes, rivers and other waterways. It crowds out native vegetation, reduces recreational opportunities, and ultimately can harm native populations of fish and other aquatic and bird species. The plant also can clog intakes where rivers and reservoirs are used for drinking water supplies and irrigation.

Task force members say the herbicide worked well on hydrilla in the treatment area last year and had little to no impact on native, non-target plants. Even so, they are advising the public not to use treated water for irrigation without consulting a task force member first.

As they did last year, task force members are contacting owners of properties adjacent to parts of the river being treated with specific restrictions and precautions regarding irrigation use, despite the fact that members are not aware of any irrigation use within the management zone.

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 found that about 25 miles of the Eno River contained hydrilla at differing densities.  The most infested area was a 15-mile stretch from the N.C. Highway 70 Bridge east of 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.”

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

The Eno River Hydrilla Management Task Force comprises a group of local, state and federal 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 or contact Mark Fowlkes at or 336-527-1547. 

Media Contact:

Jodie B. Owen


Download a high-resolution photo of the above. Please credit Tom Davis/Orange County Department of Environment, Agriculture, Parks and Recreation

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