Treatment of invasive Hydrilla to resume in Eno River

Raleigh, NC

Herbicide treatment for an infestation of Hydrilla in the Eno River will resume today and continue through September. Hydrilla is a highly destructive, non-native aquatic plant that grows rapidly and creates thick mats on the surface of waterways. 

A previous 2-year pilot study successfully demonstrated a significant reduction in Hydrilla without impacts to the rest of the ecosystem or to human health. The Eno River Hydrilla Management Task Force expanded the treatment area last year and plan to apply the herbicide to the larger area during the upcoming treatment.

The fluridone-based herbicide Sonar Genesis® will be applied in a 22-mile target zone of the river from just south of Lake Ben Johnston in the Town of Hillsborough to Roxboro Road in Orange and Durham counties. The herbicide will be applied at a level well below limits established by the U.S. Environmental Protection Agency. Property owners adjacent to the treated section of the river will be cautioned against using river water for irrigation during the treatment.

“Pesticides approved for aquatic use have passed a rigorous testing process. Fluridone is one of the least toxic among those,” said Rob Emens, program manager for N.C. Division of Water Resources’ Aquatic Weed Control Program. “At the rate it will be applied in the Eno, no restrictions on water use will be triggered except for irrigating certain plants and seedlings.” 

Hydrilla was first discovered in the Eno River watershed 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 Division of Water Resources is actively managing Hydrilla in both upstream reservoirs. Hydrilla crowds out native vegetation as it grows, reduces recreational opportunities, and can harm fish and bird species. Dense Hydrilla beds can create a toxin that is known to lead to death in waterfowl. The plant can also clog intakes where rivers and reservoirs are used for drinking water supplies and irrigation. Biologists say that since Hydrilla grows quickly and can form new plants from tiny fragments, it could become a nuisance to recreation and water supply at Falls Lake.

Keith Nealson, superintendent at Eno River State Park, looks forward to the continued success of the effort. “The task force feels great about the progress made on Hydrilla on the Eno thus far. After the next treatment is complete, we will continue monitoring the area and survey the upper watershed for potential sources, which will include working with private pond owners.”

The Eno River Hydrilla Management Task Force is a partnership of local, state and federal governments that have worked since 2007 to evaluate and address the Hydrilla threat in the Eno River. The group consists of representatives from Orange and Durham counties, Hillsborough, Durham and Raleigh, as well as representatives from state agencies that include the Division of Water Resources, Wildlife Resources Commission, State Parks and North Carolina State University. For more information on the project, visit or contact Keith Nealson at 919-383-1686 or