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Taking Over

Giant salvinia infestation
Giant salvinia by Scott Robinson, Georgia Department of Natural Resources.

Invasive plant plagues Texas and Louisiana

A natural place experienced in childhood has the power to change the trajectory of one's life. Lakes in Texas and Louisiana that are now under siege by the highly invasive plant giant salvinia (Salvinia molesta) helped define the lives of two individuals tied to the Wildflower Center.

Caddo Lake in northeast Texas offered solace to a five-year-old whose mother had died, much older brothers had gone and whose father was busy running the local general store. The child who grew up to become Lady Bird Johnson paddled the bayous there, taking comfort beneath the ancient cypress trees.

Years later in nearby northwestern Louisana, it was Lake Bistineau where 11-year-old Damon Waitt (now the Center's senior director and senior botanist) took refuge when his military family once again landed in a new place. There, he caught his first fish and later as a teen snuck his first beer.

Both individuals chose to make the environment part of their adult lives. For Lady Bird Johnson, her passions were highway beautification and the Wildflower Center that she co-founded in 1982. Waitt's experiences led to a Ph.D. in botany, the Wildflower Center and the drive to protect ecosystems from invasive species.

He recently told members of Congress and others about his enjoyment of Lake Bistineau during a public hearing aimed at thwarting the spread of giant salvinia that was held in Shreveport in June. "Like the Spanish moss draped from the cypress trees, Bistineau was draped in nature. You were surrounded by it, immersed in it and even intimidated by it, but you could by no means escape it. It is sad to think these kinds of experiences are no longer available to the 11-year-olds of 2011," Waitt said. At the hearing, he made recommendations about how to coordinate efforts to control the invasive plant.

Giant salvinia is not the only invasive plant troubling these lakes. Yet the ability of a salvinia colony to double in size in three to seven days makes it more menacing than water hyacinth (Eichhornia crassipes) and hydrilla (Hydrilla verticillata).

Water Hyacinth and Hydrilla, two aquatic invasive plant species
LEFT: Water hyacinth by Wilfredo Robles, Mississippi State University, Bugwood.org RIGHT: Hydrilla by Chris Evans, River to River CWMA, Bugwood.org. Both are invasive in some areas.

A floating Brazilian fern popular as an aquarium plant, it was probably accidentally introduced into these waters and moved from lake to lake clinging to boats and trailers. It drifts rapidly in the wind on the water's surface, leaving tiny clumps of semi-cupped leaves behind that can reproduce by budding from the attached nodes or broken stems. The white, coarse hairs on its leaves resist water and herbicides, insulate it against cold and make it stick like Velcro to boats and people. The dense vegetation the fern forms on the surface starves the water beneath for light and depletes the water of dissolved oxygen needed by wildlife.

So far giant salvinia has wreaked more havoc on Louisiana's lakes than lakes in Texas, due in part to the construction of a fence to keep the plant out of the Texas portion of Caddo Lake as well as coordinated spraying of herbicides and biological controls.

At the public hearing others who testified came from the Louisiana Wildlife and Fisheries Department, U.S. Geological Survey, U.S. Army Corps of Engineers, Louisiana State University's Idlewild Research Station, Caddo Lake Institute and National Fish & Wildlife Foundation. They joined Waitt in speaking before Subcommittee Chair John Fleming (R-LA) and Rep. Louie Gohmert (D-TX).

Dr. Waitt urged those involved in addressing the spread of this plant to integrate their efforts by establishing a Cooperative Weed Management Area. CWMAs are local partnerships that coordinate efforts to address the threat of invasive plants across jurisdictional boundaries. They include local citizens, city, county, state and federal leaders, and both nonprofit organizations and for-profit corporations.

"Because CWMAs cross geographic and political boundaries, groups that have an agreement in place can address invasive plants on the landscape as a whole, rather than piecemeal," he said.

Watch footage from the public hearing here