Linda Benedict, Van Osdell, Mary Ann | 7/20/2011 12:04:17 AM
SHREVEPORT, La. – A Brazilian weevil that feeds on giant salvinia is a biological control for the invasive species that has been taking over water bodies in Louisiana since it was first discovered in the state in the Toledo Bend reservoir in 1999.
Dearl Sanders, LSU AgCenter weed scientist, gave testimony on how the weevil works at a Congressional Natural Resources Subcommittee hearing led by U.S. Rep. John Fleming, R-La., and U.S. Rep. Louis Gohmert, R-Texas, at LSU-Shreveport on June 27.
Sanders was invited to offer their ideas for control or eradication strategies of the invasive species and costs involved.
Giant salvinia spread from Brazil to many areas of the world in the 1950s and 1960s. Experts have employed several control measures, including herbicide sprays, mechanical control, booms, drawdowns, educating the general public and weevils. The LSU AgCenter has been investigating control measures for giant salvinia since 1999, Sanders said.
In partnership with the Louisiana Department of Wildlife and Fisheries, the LSU AgCenter helped collect and transport more than 30 tons of weevil-infested giant salvinia with approximately one million weevils to Lake Bistineau near Bossier City and four other north Louisiana lakes in 2009.
Sanders said the weevils have reduced salvinia 90 percent in some areas in south Louisiana, but they have not survived the cold winters in the Shreveport area. He said research needs to be directed on finding a strain that can accommodate low winter temperatures.
The LSU AgCenter has helped establish weevil nurseries in Lafourche, Terrebonne and St. Charles parishes. The initial weevil nursery in Gheens was used to develop the protocol for salvinia and weevil production, the timeline for weevil population growth and the optimum times for weevil harvest and distribution.
Sanders noted that weevils don’t fly. "This is important in planning a distribution system, since any movement of weevils from one place to another that is not directly connected by water is unlikely," he said. "Man has to move them from point A to point B, and it is labor intensive."
Sanders also has conducted an extensive grass carp biological control study that confirmed that grass carp will not eat giant salvinia even when it is the only plant available. "Grass carp only eating giant salvinia died," Sanders said. "Giant salvinia contains a metabolic toxin."
Sanders said it was "the nastiest trial I ever ran in my life."
Mary Ann Van Osdell
(This article was published in the spring issue of Louisiana Agriculture Magazine.)