Officials: Bio-control efforts making progress against salvinia at Caddo Lake

Gary Kempf’s boat cuts a path through the giant salvinia floating on Caddo Lake as he leaves the Crip’s Camp Marina in this June 2017 photo. Kempf says the secret to not getting stuck in the blossom is to keep the boat’s prop as low as possible without hitting the bottom of the lake.

MARSHALL — The invasive giant salvinia plant is under control and seeing a dramatic decrease at Caddo Lake thanks to the efforts of the Uncertain Morley Hudson Weevil Greenhouse in conjunction with the Texas Parks & Wildlife Department.

“We had a great winter last year that reduced the amount of salvinia,” said Tim Bister, the local representative of Texas Parks & Wildlife. “In 2017, we had over 5,000 acres of giant salvinia on Caddo and reduced the number to about 1,300 acres when we did our survey this past August.”

Giving an update of local mitigation efforts, at the request of Harrison County Judge Hugh Taylor, Daren Horton, president of the Caddo Biocontrol Alliance, thanked the Harrison County Commissioners Court at its meeting Wednesday for the county’s early and continual support of the biocontrol alliance and the efforts with the weevil greenhouse to maintain the progress on Caddo Lake.

The alliance operates the biocontrol-based giant salvinia management program.

The court voted to contribute $2,000 to Cypress Valley Navigation District to assist in control efforts at the lake.

“The giant salvinia is one of the most aggressive aquatic species in the world, and when we saw that this needed to be taken care of, we started a grassroots effort from individuals and municipalities and entities — anywhere that we could get funding to start the greenhouse,” Horton said.

Giant salvinia, a highly invasive aquatic fern that’s native to southern Brazil, was first found on Caddo Lake in 2006. To help combat the plant, the state of Texas invested millions into an aquatic herbicide spraying program.

For further eradication efforts, the Uncertain Morley Hudson Weevil Greenhouse opened in August 2014 as the first high production weevil rearing facility in the world as well as a biocontrol-based giant salvinia management program for Caddo Lake.

And because of the support from the county and other entities, they’ve had a successful project, Horton said.

“We’re optimistic about the future and what we want to achieve,” Horton said. “We’re also excited about the strong possibility of expanding into another greenhouse in 2019 through cooperation with the Caddo Lake Institute and all the entities that work with us.”

He said they were able to transfer some weevils back to Texas Parks & Wildlife this past year.

“We had in excess of 30 hours in a row of freezing temperature, which really knocked the plant (out),” Horton said. “So going into this year, we didn’t have salvinia out there to put the weevils out, but there were other areas in Texas where they don’t have climate-controlled greenhouses. They needed weevils in different lakes in Texas, so they actually purchased that from us and put it in other lakes in Texas.”

Laura Speight, a retired Parks & Wildlife biologist who was hired as the new greenhouse manager in April, credited the many volunteers for helping make the program a success.

“From April through November, we’ve had over 450 volunteer hours. This is basically people — not just from Uncertain, but people from Atlanta, (around) Harrison County (and) Marshall,” she said. “Sometimes we have tourists who come in and give an hour or two or three.”

She said the grassroots effort shows how much people care about Caddo.

She said that for the fiscal year Sept. 1, 2017, through Aug. 31, 2018, the greenhouse had a record year, releasing 200,378 weevils.

“That’s the most we have ever done,” Speight said.

And since the start of the new fiscal year, which began Sept. 1, the greenhouse already has released 30,000 weevils.

She said the adult weevils were released in five locations in 2018: Willowson’s Woodyard, Benefield Pond, Hay Rake, Dorough Island Canal and Pine Island Slough.

“These are the backwater areas,” she said, noting a total of 177,881 weevils were released, with the last release on Nov. 10.

TPWD partnership

John Findeisen, coordinator for the invasive species control program at TPWD, announced that Parks & Wildlife has increased -ts contribution to CBA from $20,000 to $50,000 this year.

“Of course, $20,000 of that will be used for the improvements and expansion of the current greenhouse,” he said.

Findeisen, who oversees all the herbicide contractors as well as contracts for the salvinia weevil greenhouses that TPWD has in Karnack and Brookeland, said they were grateful for the weevils given to the agency by CBA for other lakes.

“We definitely used them,” Findeisen said, noting TPWD used the weevils on Lake Naconiche and Lake Nacogdoches.

Other Invasions

Bister said when salvinia is reduced, other species, such as the nonnative hydrilla, increase.

“The acres went from 1,800 acres in 2017 to 4,700 acres this year, because it wasn’t getting shaded out by the giant salvinia,” he said. “So it’s a game that we have to play from year-to-year and see which species are the more problematic.”

Bister said another new plant has been sighted for the past few years on Caddo called the crested floating heart.

“If you’ve spent any time at the lake, you see these white flowers that almost look like it’s snow, and that’s a species that’s pretty hard to manage,” he said.

Horton said giant salvinia will most likely be a management program indefinitely.

“It will never go away,” he said. “And we’re still learning. We’re in the early stages. We’re optimistic about the cold-tolerant weevils from Brazil that were found up in the mountains.”