Researchers continue quest to eradicate salvinia from all Louisiana waterways

The LSU AgCenter is moving its facility for growing weevils to eradicate the aquatic weed called salvinia.

A location in Terrebonne Parish on the property of Michael St. Martin had been used for the past four years.

“We appreciate the St. Martin family for allowing us to establish a weevil population on their land,” said Rodrigo Diaz, LSU AgCenter entomologist. “It provided an excellent location to maintain a healthy population of the insects.”Diaz said three new locations will be used, all on LSU AgCenter property.

Salvinia is an invasive species that came to the U.S. in the 1990s from South America. It grows rapidly and forms dense mats on the water surface. Herbicides can be used to control salvinia, he said. But spraying is not completely effective, and enough plants survive to maintain a regrowth of the invasive species. The weevils are originally from South America, too. “They are not good fliers, and they won’t move to crops,” Diaz said. “These weevils only attack salvinia.”  

Dearl Sanders, who ran the LSU AgCenter weevil program before retiring last year, said the weevil project for large-scale releases began at Gheens in 2008, and the weevils were harvested and released from that site through 2011.  

“Most of the success was achieved in the Lafourche, St. John, St. Charles and Jefferson parishes,” Sanders said. “On monitored sites in Lafourche Parish, infestation levels of giant salvinia were reduced by 90 percent within three years.”   Sanders said the weevil nursery was moved to Houma in 2011, and salvinia populations had been reduced by 90 percent in that area.  

Diaz said salvinia remains a problem in Cameron and Vermilion parishes. In addition, the weed is a big problem in lakes and streams in central and north Louisiana, such as Cross Lake near Shreveport and Lake Bistineau near Doyline.  

But the weevils have difficulty surviving cold winters, so new strategies are being used to help maintain the insect’s population in north Louisiana.  

Research by another team member, Steve Micinski, is being done using pine straw and fabric to cover infested salvinia to help insulate weevils from the cold.  

Seth Johnson, LSU AgCenter entomologist, said controlling salvinia with weevils on Cross Lake and Lake Bistineau has been inconsistent because of cold winters. “Control on those two lakes has been seasonal and intermittent with elimination or near elimination of the weevil population in three of the last five years due to winter temperatures below survival levels,” he said.  

Johnson said another research project is in progress to find weevils in southern South America or Australia that can tolerate the harsh winter temperatures that occur in north Louisiana.  

Bruce Schultz is a writer and photographer with LSU AgCenter Communications.

The summer 2015 issue of Louisiana Agriculture magazine includes articles on a variety of topics that affect Louisiana’s agriculture industry and the environment – water management at Catahoula Lake, 4-H youth wetland programs, artificial reefs for water conservation, corn nitrogen management in saturated soil conditions, and more. 36 pages

9/16/2015 10:16:34 PM
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