Herbicides Winning Against Invasive Aquatic Weeds

Published July 1, 2005

Buoyed by recent successes in the battle against invasive aquatic weeds, the Virginia and North Carolina communities surrounding cross-border Lake Gaston are turning to precise herbicide spraying to eliminate nuisance weeds. But difficulties in coordinating a multitude of government agencies threaten to slow the pace of clean water progress.

Hydrilla Invades Lake

Lake Gaston straddles the border between North Carolina and Virginia and is the largest body of water in the central border region. Lake Gaston is not only beautiful, but it has been one of the most prolific freshwater fishing holes along the Atlantic seaboard.

In the 1980s, however, a voracious invasive weed known as hydrilla took root in the lake. Native to Africa, hydrilla was imported to the U.S. for use in freshwater aquariums. In 1960 hydrilla was spotted growing in the wild in Florida. Since then, it has spread to much of the southeastern U.S.

Hydrilla is a submerged weed that takes root at the bottom of shallow water and sends spindly stems of vegetation to the surface. It forms a thick, dense manse of vegetation that is virtually impenetrable by boats, fish, and human swimmers. Hydrilla crowds out native vegetation, deprives fish of oxygen, blocks irrigation and drainage canals, harbors bacteria that cause human and animal diseases, and makes human recreational activities dangerous or impossible.

Herbicides Only Solution

Since 1985, the Lake Gaston Weed Control Council has fought a largely unsuccessful battle against hydrilla. Carp have been used to try to control the weed, but the fish eat beneficial weeds along with hydrilla, and their numbers cannot be controlled once introduced to the lake.

“We’ve got a severe problem, and it has got to be brought under control, and it’s going to get worse if we don’t do something,” Halifax County, North Carolina commissioner J. Rives Manning Jr. told the Richmond Times-Dispatch.

According to the Times-Dispatch, however, “reinforcements have arrived” in the form of Aquatic Nuisance Plant Control, a company retained by the Lake Gaston Weed Control Council to treat the hydrilla with precise applications of herbicide.

Fishermen Pledge Support

At first, fishermen opposed the use of chemical applications to treat the weeds. Fearing the chemicals would harm the lake’s fish, “no matter what we did, they were vocally against it,” Elton Brown, chairman of the Weed Control Council, told the Times-Dispatch.

Open meetings, education, and a history of successful chemical application, however, have turned local opposition into support.

“Whenever I used to hear the words ‘chemical spraying’ in relation to bass fishing I would be ready to get in the ring and put up my dukes,” conceded Virginia B.A.S.S Federation State Conservation Director Ted Phipps on the group’s Web site, after attending a Lake Gaston Weed Control Council meeting.

“To my surprise,” wrote Phipps, “there were fishermen on the weed control council. They were actually nice people that had a problem and were doing the best they could to handle it. I was enlightened to find that the chemicals that are being applied aren’t harmful to the fish at all if applied correctly.

“They are the most cost-effective solution to the problem as well. Other methods have been tried, but have failed,” Phipps added. “The sprayers are calibrated to make sure they do not over spray and the boat operator is a graduate of N.C. State with a degree in fisheries.”

“Pesticides safety standards ensure the public is exposed to pesticides and herbicides only at levels that are thousands–and usually tens of thousands–of times less risky than the exposure amount EPA concludes is safe,” noted Angela Logomasini, director of risk and environmental policy at the Competitive Enterprise Institute.

“Pesticides and herbicides are specifically designed to address target organisms, which they can affect at very low levels–exposing the public to only trace levels and ensuring no significant public health impacts,” Logomasini continued. “Accordingly, we can use these products to solve serious pest problems–that threaten our health and environment–while posing little risk to the public and non-target species.”

Houghton Lake a Model

The Weed Control Council expects the herbicide treatment to achieve results similar to those achieved by Michigan’s Houghton Lake treatment program. During the 1990s in Houghton Lake, invasive Eurasian watermilfoil began taking over Michigan’s largest inland body of water, devastating the native ecology of the lake as well as the region’s tourism-based economy.

In 2002 lake managers treated the weeds with the aquatic herbicide Sonar. A post-treatment survey of area residents conducted by the U.S. Army Corps of Engineers, the Houghton Lake Improvement Board, and SePRO (the company that manufactures Sonar) revealed outstanding results.

According to the survey, 95 percent of Houghton Lake area residents were either “satisfied” or “very satisfied” with the chemical treatment. Fully 70 percent of area residents would choose the same course of action if the problem recurred, while only 7 percent said they would not. (The remaining 23 percent had no opinion.)

James M. Taylor ([email protected]) is managing editor of Environment & Climate News.

For more information …

The July 2004 Economic Impact Survey of Eurasian Watermilfoil Removal from Houghton Lake is available online at http://www.sepro.com/documents/Houg_Eco_Impact.pdf.