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Water mower helping fight giant salvinia

Fighting giant salvinia on Lake Bistineau has become a battle on many different fronts, and one of those ways could be through an improved water mower.

John Bourque, who patented the water mower, has been on the lake since Monday with the improved version at Port O Bistineau. He says he is conducting a five-day test to see what the water mower will do.

“It picks it up, grinds it to a pulp and it will sink to the bottom of the lake and it cannot regenerate,” he said. “We can cut from one foot to one inch deep. When we cut it, you see the water again.”

One of the benefits, he says, is there is no use of chemicals on the lake. Also, when he cuts it, it’s cut inches deep, and herbicide spraying can only kill the top; it’s not getting to the roots, he said.

The drawdown of Lake Bistineau is expected to begin Monday, and Bourque says he’s cutting the salvinia close to the drawdown to try to help the Louisiana Department of Wildlife and Fisheries.
“We can get in there and help Wildlife and Fisheries,” he said. “They can spray and we can cut. Whatever tool we can use against this salvinia, really it’s a cancer. It just grows. The only thing we’re trying to do is help our lake, because I live on Lake Bistineau. What we’re trying to do is get everybody to work together to come up with something that’s helping.”

The water mower has been redesigned, Bourque says, and is less time consuming. The boat is about eight foot wide by 28 feet long, he said.

He says during the first two days of testing, he’s covered 150 acres of the lake. There is no accurate measurement of what it would cost in fuel or maintenance as he is in the early stages of testing, he added.

Jeff Sibley, biology manager for Region 1 for LDWF, says a study on the water mower did not seem to help.

“It has not been proven economically viable to use on a large scale, but it is another tool to use,” he said.

According to the 2013 study conducted by LDWF, in a controlled setting, results showed that within 19 days of mowing, the salvinia returned with a vengeance.

The study was done off the boat launch at Lake Bistineau State Park in a 4.5-acre area.
Sibley explained that salvinia is 95 percent water. The plant likely will not reproduce by spores alone. It can be reproduced through fragmentation, which means the plant is broken up and continues to grow from those broken pieces.

“It can regenerate by small pieces if that reproductive node is still intact,” he said. “The research, the science says the spores on the plant are sterile. The plant reproduces by vegetative means, so any small fragment can grow into new plants.”

With the mower chuting the pulp back into the water, the pulp sinks to the bottom of the lake.
Sibley says it’s a two-fold battle between the salvinia and the organic buildup. The only way for the salvinia to completely decompose is to allow it to dry out, he said.

The drawdowns create a condition which allows oxygen to reach the organic material at the bottom of the lake to complete decomposition.

Research into another way to get rid of salvinia is currently underway. A couple that lives on Lake Bistineau has purchased a barge they are turning into a salvinia harvester. The idea is to pull the entire plant out of the lake, deposit it onto a barge, and then haul it somewhere to dry out and decompose.

The water mower cuts giant salvinia anywhere from one foot to an inch deep, grinds it to a pulp and it chutes back into the water, sinking to the bottom of the lake. Courtesy Photo
The water mower cuts giant salvinia anywhere from one foot to an inch deep, grinds it to a pulp and it chutes back into the water, sinking to the bottom of the lake.

Weldon Thomas says they will have a barge in which to deposit the harvested salvinia beside the harvester.

“We will have a barge pulled up to the side of us, so when one gets full, it will take off and another one is pulled up beside us,” he said.

Private property has been donated as a final place to deposit the salvinia.
Sibley says no matter what is done, salvinia has been a difficult plant to kill and control.

“Its growth potential is its greatest strength,” Sibley said. “Whatever you do to control it today, in a short period of time, it has recovered. The larger area you are trying to control, with this plant, the more difficult it becomes to control.”

The goal by all parties remains the same: control the salvinia so that everyone can enjoy the lake.

Minden Press-Herald

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