Giant Salvinia: The non-native plant in Louisiana waters

LAKE CHARLES, La. (KPLC) - On the surface, it seems like just another plant, when in reality, it’s anything but.

Originally from Brazil, giant salvinia has made it’s way across the world, including into Louisiana’s waterways and the plant can have some serious impacts on wetland ecosystems.

According to the LSU Ag Center, giant salvinia was found in the Toledo Bend Reservoir in 1998.

“For the last few years, we’ve been fighting it,” Dean Kelly, the Director for the Calcasieu Parish Police Jury Facility Management Department, said. “It’s a very invasive aquatic species.”

“I get phone calls every day," Kevin Savoie, Area Agent for the LSU Ag Center, said. "Land owners, land managers, and marsh managers asking for help or assistance.”

The aquatic weed can completely cover waterways in a matter of weeks.

“It can double in size every five to seven days under the right growing conditions.” Savoie said. “When it first showed up in Cameron, it was amazing. There was a drainage lateral north of the Cameron Courthouse called W1 West. It completely filled that canal when the water flowed and totally blocked the drainage. Some local workers actually got out on top of it, in an 8 foot deep canal, and walked across it. It would just roll with the current and was stacked. It was bad and we had no way to stop it. And we will never be rid of it now. It’s here to stay."

Those conditions being a hot and humid climate like Louisiana’s. Officials these nonnative plants can have some serious impacts.

“So as it continues to grow it can actually create a matte about three feet deep and it completely chokes out the sunlight and completely take over a body of water.” Kelly said.

“Which prohibits draining, boater access, it also covers that water column and prevents sunlight from penetrating down, therefore reducing fisheries production and wildlife production, growth of water fowl foods and other things that are really important to us on the coast," Savoie said. "So it has huge implications.”

In Calcasieu Parish, the Holbrook Park Pond is one of the affected bodies of water in the parish by salvinia according to Kelly.

“Once you have it, it’s very hard to truly eradicate it, so you just want to stay on top of it," Kelly said. “You have to be vigilant. We do have a spillway that comes out of this part and winds up into the river, so it’s very important to keep that under control so we don’t allow this to escape the pond. There are a couple of methods to deal with it. The first method you try to go with is mechanical. Where you remove it with rakes, pitchforks, and whatnot. You just physically drag it out of the water to get it off it. As long as it’s in small masses you can do that and it’s fairly effective. If the mass gets too big, that’s no longer effective and it becomes very expensive. You have herbicide treatments. Anytime you are dealing with salvinia you want to kill it slowly. If you have too big of a die off to fast and you have too big of a mass of decaying matter in your body of water, it depletes the oxygen. When that happens you kill all the fish in that body of water. But we have been able to manage it and we are at that point now to where we have it pretty well under control. But we need to take that next step to make sure we keep it under control.”

Kelly says the Calcasieu Parish Police Jury recently approving a right of entry and maintenance agreement with area landowners, which allows staff and contractors access to the shoreline of the pond located on private land.

“When you look around the pond, you see the body of water is open,” Kelly said. “But along the edge, tucked up into trees and along the bank you can see pockets of this salvinia. That’s where we really need to target it now. In order to do that we needed permission, we needed to have those agreements in place. So now our approach is to assess those areas and mechanically remove what we can.”

In Cameron Parish, Savoie says the LSU Ag Center believes they may have found a solution for the Parish in a little bug called a salvinia weevil, native to Brazil. Kelly says they will use the weevils in targeted areas in Calcasieu as well.

“The weevil that was introduced to control this plant is very specific to this plant," Savoie said. "It won’t feed on any other plants. That little hole is where an adult weevil went through feeding.”

Savoie says that giant salvinia has invaded all of the waterways in Louisiana, meaning if an area in north part of the state can’t control the giant salvinia, it could potentially make it’s way back to Southwest Louisiana. So while the weevils are not the perfect solution, it’s working for Cameron Parish for now.

“This one is here to stay," Savoie said. "We aren’t going to get rid of it now, but that’s a good option for us right now, to help control the plant.”

Savoie says if you live in Cameron Parish and have an infestation to find weevil-infested salvinia and transfer it to their area.