James Seales, left, and Kevin Houston, both biologists with the Louisiana Department of Wildlife and Fisheries, helped control the salvinia plant in Lake Bistineau by releasing in 2009 the salvinia weevil, which eats the plant. (Photo by Johnny Morgan. Click on image for downloadable version.)

News Release Distributed 04/05/10

SHREVEPORT, La. – An LSU AgCenter weed specialist says managing an invasive aquatic weed known as giant salvinia by erecting a floating fence on a narrow point of Cross Lake may only be a short-term solution to stopping the fast-growing plant from clogging the waterway, threatening the water supply and harming fish.

“In my experience, a floating fence is an effective, but short-term solution,” said Dearl Sanders, weed specialist at the Bob R. Jones Idlewild Research Station in Clinton. “The fence must be inspected and maintained. A single rip or tear in the material will result in spread of the plants.”

A fence is most effective when used in combination with a herbicide application program because the fence confines the plants to a certain geographic area and repeat applications are more effective, Sanders said.

Giant salvinia is a true floating plant and does not attach itself to any substrate, Sanders said. “Without the barrier, a spray program requires the plant to be chased across the lake, making repeat applications difficult.”

Sanders and other scientists at the LSU AgCenter, in cooperation with the Louisiana Department of Wildlife and Fisheries, have been involved in a salvinia eradication program since the weed was found in Toledo Bend in 1999.

One project has involved the rearing and releasing of salvinia weevils that eat the plant, which grows in thick mats and clings to boat motors and trailers. Salvinia populations double in size every day.

The resilient South American aquatic plant has invaded many lakes in northwest Louisiana, Sanders said. He brought the weevil to Lake Bistineau in June to control the weed there.

“Caddo Parish has some experience with the problem,” Sanders said. “Local public works folks have been heavily involved with the problem on Caddo Lake,” he said.

“Along with the weevil program, we continue to evaluate new and older herbicides for effectiveness,” Sanders said.

City officials plan to meet Tuesday with lakefront property owners to discuss the fence and other options.