Mike Turner sprayed herbicide recently on the weed Salvinia molesta on Caddo Lake near Uncertain, Tex. The weed suffocates all life beneath it. The furry green invader from South America is threatening to smother the labyrinthine waterway, the largest natural lake in the South, covering about 35,000 acres and straddling Texas and Louisiana. Blumenthal, R. July 30, 2007. In East Texas, Residents Take On a Lake-Eating Monster. New York Times. Photo credit: Michael Stravato.