Conservation Matters August 2012

The Texas Land, Water and Wildlife Connection

Congressman Gohmert visits Caddo Lake and giant salvinia weevil-rearing facility

By Kathy Wythe

Congressman GohmertCongressman Louie Gohmert of Texas and many members of his staff recently visited the Center for Invasive Species Eradication’s giant salvinia weevil-rearing facility at the Caddo Lake National Wildlife Refuge in East Texas, according to Lucas Gregory, a Texas Water Resources Institute (TWRI) project manager.

Dr. Allen Knutson, Texas A&M University professor, Texas AgriLife Extension Service entomologist and lead researcher at the facility; Lee Eisenberg, AgriLife Extension assistant; and Gregory gave the Congressman an overview of giant salvinia, a free-floating aquatic fern native to South America, and the center’s research program on managing the invasive plant with biocontrol, using giant salvinia weevils, and chemical application.

"In 2012, we have released 51,000 salvinia weevils on the lake and sprayed approximately 640 acres with chemicals. The Texas Parks and Wildlife Department has sprayed about 400 acres, and Cypress Valley Navigation District has sprayed another 350-400 acres," Gregory said.

Giant salvinia has invaded water bodies in the southern United States in recent years. Caddo Lake was first infested with giant salvinia in 2006.

"The flood and freezes in the winters of 2010 and 2011 greatly reduced the amount of giant salvinia present in Caddo Lake, but it has come back with a vengeance this year," Gregory said. "Although we don’t have an accurate estimate of infested acreage, giant salvinia is present and thriving throughout the upper portions of the lake."

Caddo LakeThe center, part of the Texas AgriLife Extension Service, Texas AgriLife Research and TWRI, operates the weevil-rearing facility, located near the refuge headquarters.

"We toured the greenhouse where the weevils are growing and informed the Congressman and his staffers about the project partners that are involved and the support we have received from agencies and from landowners around Caddo Lake to get everything built," Gregory said.

In the laboratory, Eisenberg explained how weevils are sampled and counted, and the Congressman and his staff had the opportunity to see an adult weevil and larvae under the microscope.

The group also presented biocontrol results and other efforts being conducted at the center, such as cold tolerance studies, dispersal studies and efforts to get more cold-tolerant weevils to the facility.

Gregory said the cold tolerance studies are determining how the salvinia weevils adapt to cold weather and which ones are better suited to the climate at Caddo Lake. They are using weevils grown at four different locations: the Lewisville Aquatic Ecosystem Research Facility in Texas, Louisiana State University, University of Florida and Australia. They are comparing the three from the United States to the quarantine weevils directly from Australia that the U.S. Department of Agriculture Agricultural Research Service acquired for this particular study.

Gregory said early results of the cold tolerance studies indicate that the weevils direct from Australia might be better suited to Caddo Lake.

"We hope to get some weevils from Argentina by December through the U.S. Department of Agriculture-APHIS to do only laboratory tests at Texas A&M," Gregory said. "Because of the higher elevation of Argentina, we expect these beetles to be more cold tolerant than those from Australia."

The visit concluded with a viewing of a video taken by Jack Canson of the Caddo Lake Institute and Robert Speight of the Cypress Valley Navigation District at the end of July that shows how extensive giant salvinia growth is on parts of the lake.

The Caddo Lake Giant Salvinia Eradication project is funded by Congressional support through the USDA Natural Resources Conservation Service.

Back to Top