Water kudzu attacking Claytor Lake

By Marty Gordon

RADFORD – Lurking below the depths of Claytor Lake is a fast-moving aquarium plant, and a biologist with the Virginia Department of Game and Inland Fisheries is worried about how much of the lake is being swallowed up by the “water kudzu”–commonly known as Hydrilla.

The plant hampers swimming, and tangles props and sailboat keels. The later is what worries Biologist John Copeland.  “It’s slowly becoming a problem with boating and navigation,” he said earlier this week.

FOCL photo Hydrilla, an invasive Asian water plant, is choking an estimated 400 acres of Claytor, already causing boating and swimming problems.
FOCL photo Hydrilla, an invasive Asian water plant, is choking an estimated 400 acres of Claytor, already causing boating and swimming problems.

Back in September, it covered an estimated 400 acres, up from 40 in 2003.  Early estimates say it could grow to 1,000 in a very short time.
Claytor encompasses nearly 4,000 acres, and the biologist reminds everyone to check their boats and trailers when they leave the water. “A few sprouts,” Copland said, “can spread the plant to other waterways like the New River or Rural Retreat Lake, and then it will appear in other spots.”

Hydrilla is a non-native invasive Asian water plant introduced to North American waterways in the 1960’s as an aquarium plant. It tolerates low-light, thriving in shallow water, but is found as deep as 300 feet. Copeland says the plant’s potential on the recreational use of the lake may be significant.

Because it quickly grows from the bottom to the surface, displacing other plants by shading, Hydrilla can choke off entire coves and shallow areas of the lake. It can become the primary aquatic plant in Claytor Lake in areas where it finds suitable soils.

Initially, acccording to facts supplied by the Friends of Claytor Lake (FOCL), anglers love Hydrilla and don’t want to see it destroyed, because catching fish along the edges of large Hydrilla beds is often easier than catching them in other habitats.  Left untreated, Hydrilla spreads quickly, choking out available fish habitat and interfering with predators feeding on prey, resulting in unbalanced fish populations. Hydrilla can also cause oxygen sags in the back ends of coves, resulting in fish kills.

In some cases, Hydrilla serves as a surface for a species of toxic blue green algae that can kill waterfowl that eat the plant or predatory birds (like bald eagles) that eat waterfowl.

Last year, the state stocked grass carp in and around the heavy Hydrilla areas, and Copeland feels the carp got the ball rolling in controlling it naturally.  “That’ s helped as several of the fish we tagged have increased in size.” Another stocking is planned for April.

In addition, the agency in cooperation with American Electric Power used a chemical spray (Komeen) at several areas where the plant has appeared. “The chemical treatment has also helped, and we plan to do more of that in the near future too,” said Copeland.

He admits eradication is usually not possible, but controlling it is the goal through a combination of mechanical harvesting, chemical control, and long-term biological control with the carp.

Clearly, the unchecked growth of Hydrilla in Claytor Lake has potential long-term impacts on many lake users.

FOCL says, “If we fail to address this resource management problem, the use of this important southwest Virginia reservoir will be impacted for years to come.  We must determine ways to control this ‘Hydrilla Gorilla’ before it overpowers Claytor Lake.”

A common quote is that “Hydrilla can grow an inch per day”.  In an Army Corps of Engineers study about optimal growth conditions, it was found that hydrilla grew 3200 or 3400 inches in 32 days.

In the very near future, Pulaski County hopes to obtain a grass carp stocking permit of its own from the VDGIF and purchase 6,000 triploid grass carp that are a minimum of 13 inches long which will be dumped into the lake.  The VDGIF aquatic biologists will tag an adequate quantity of these fish with radio transmitters to track the fish and monitor their effectiveness. Copeland says a third stocking might have to be done in hopes of an overall Hydilla reduction.