Giant Salvinia

Giant Salvinia

Photo Credit: USFWS

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Giant salvinia is a free-floating aquatic fern native to central South America.  Its explosive growth characteristics have had devastating impacts on resources in Africa, Australia, New Guinea and Sri Lanka where the plant has been inadvertently released. Introductions of co-evolved, predatory weevils (Crytobagous salviniae) from South America successfully controlled giant salvinia in many locations. In 1998 giant salvinia was recognized as a U.S. problem when it resisted eradication efforts in a small schoolyard pond being used for aquatic resource education near Houston, Texas. Biologists suspect it was introduced to the demonstration pond as a contaminate hitchhiking along with aquatic plants purchased from an aqua garden distributor. Although giant salvinia was listed as a federally prohibited noxious weed in the 1970s, it was still readily available as an aquarium plant and used in aqua gardens.

Soon after giant salvinia’s appearance in Houston, it was being reported in Toledo Bend, Lake Conroe and the lower Trinity River in Texas and Bayou Teche in Louisiana. Its original spread to open water was likely as an escape from horticulture. A study by USDA found giant salvinia being cultured in sixteen states. Once established, boaters became the primary pathway to spread this prolific and hardy aquatic nuisance species to other waters. Efforts to control giant salvinia in the schoolyard demonstration pond were eventually abandoned and the pond was filled.