STEPHENSVILLE, La. (AP) — A researcher says the hard winter apparently killed much of an invasive weed that clogs waterways around Louisiana — but it also killed many of the weevils raised to fight it.

LSU AgCenter researcher Charlie Wahl says few north Louisiana landowners or agencies have asked for weevils to eat away at giant salvinia .

Giant salvinia is a South American water fern imported for aquariums and ponds. The problem arose because people who didn't want it any longer dumped it into waterways. It grows so fast that it can form thick mats, hindering boat travel and blocking sunlight from water plants, including those that serve as food and habitat for waterfowl.

"Instead of seeing our normal infestations in late spring, we are now moving into summer before we saw our giant salvinia create big mats to where they are problematic for waterways," Wahl said in an AgCenter news release.

But he said the salvinia weevils he's farming and those in the wild around the state also were knocked back, and are starting to reproduce later, too.

He recently released salvinia weevils in the Big Fork Bayou area near Stephensville. But he says those take months to begin to show effects, and landowners or state agencies may need herbicide to curb the plant in time for teal season.

"Relying on just chemical control alone is very costly, and it is a short-term, small-scale solution to the problem," Wahl said.

Landowners interested in getting weevils to fight giant salvinia on their property should contact their local Soil and Water Conservation office, Wahl said.