Herbicide treatments to kill an invasive plant called hydrilla in the Eno River have proven successful so far, but officials are having trouble securing money for a second round of treatment.
A task force of government agencies, nonprofits and researchers from N.C. State University began the two-year project to eradicate the hydrilla plant last May. They released the herbicide fluridone into a 16-mile stretch of the Eno River throughout last summer and have been monitoring the chemical’s effects. The latest tests show a reduction in hydrilla with little effect on other plants and animals.
The first round of herbicide treatments cost around $75,000, about half of which came from the N.C. Division of Water Resources. But the latest appropriations bill from the General Assembly states that money from the division can be used only for projects in lakes, not rivers, meaning other partners in the task force are being asked to contribute more.
Edward Buchan, Public Utilities Administrator for the city of Raleigh, said the Eno River Hydrilla Management Task Force asked each of the seven funding partners to pay $2,110 more this fiscal year. He said some of the partners, which include the city of Durham, Orange and Durham counties and Hillsborough, might have a hard time finding extra money in their budgets.
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“But everybody has agreed in principle, and they’re now working through getting things signed,” said Buchan.
Hydrilla is a spiny plant native to Asia that grows in thick blankets beneath the water’s surface. The invasive plant reduces water flow, creates water quality problems and harbors bacteria that can kill aquatic birds and bald eagles. Hydrilla is illegal to transport, grow or sell in North Carolina, but is often accidentally transported when stuck to boats or fishing equipment.
“It grows like crazy,” said Mark Fowlkes of the N.C. Wildlife Resource Commission. “This stuff makes kudzoo look like nothing.”
The herbicide treatment was cut off early last year due to concerns about secondary impacts on the Eno River’s native wildlife. But further testing proved that the herbicide had no adverse effects on even the most sensitive wildlife, such as freshwater mollusks or water willow plants, but it did keep the hydrilla under control.
“To some degree, the chemicals are safe beyond expectation,” said Charlie Peek, a spokesperson for the N.C. Division of Parks and Recreation.
Fowlkes said that the herbicide does not harm animals or humans. The main concern is using Eno River water for irrigation, because the herbicide might discolor or damage other plants.
The herbicide treatment is often used in reservoirs, but Fowlkes said that it has not been used before in a North Carolina river like the Eno. The task force hopes the research on how to manage the Eno’s hydrilla with herbicides could be applied to other rivers. Previous efforts to remove the plant by hand failed because hydrilla can break into fragments and regrow easily.
The task force chose to use herbicides rather than more extreme methods such as introducing grass carp to the river, which would eat the hydrilla but also eat native plants.
“That’s kind of a sledgehammer approach,” said Fowlkes, “We want to manage it before it gets to that level.”
Raleigh is part of the task force to try to prevent hydrilla from moving into Falls Lake, Wake County’s largest source of drinking water. In addition to disrupting boating and swimming, hydrilla can clog pipes that transport drinking water.
Hydrilla has been moving downstream toward Falls Lake, but no patches have been detected in the river beyond U.S. 501. Fowlkes said researchers have found fragments of the plant in Falls Lake, some of which can still grow into full plants seven years after breaking off.