Invasive Aquatic Weed Threatens Lakes, Waterfowl Hunting

An invasive aquatic weed recently arrived to the U.S. could change the face of waterfowl hunting and fishing and have far-reaching impacts to the economy. Salvinia molesta, also called giant salvinia, was first discovered in the U.S. in 1995. Today it’s found in 12 southern-tier states from California to North Carolina; coastal inland waters of Oregon and Washington are at risk of infestation. Unabated, Salvinia molesta could impact our economy by causing irreparable damage to the environment, affecting hunting and fishing, farming and hydropower.

Salvinia molesta floats on the water surface and grows at phenomenal rates, doubling the area it covers in less than a week. Mats of Salvinia molesta may reach three feet thick blocking sunlight to waters below killing beneficial plants, bugs, and fish. Small lakes could be covered in a matter of days, water works clogged, and eradication is no easy matter.

Mechanical removal is nearly impossible given the dense mats weigh around 36 tons/acre; shredding plants is not effective either given the plant’s ability to continue to grow from the smallest living portion. Herbicides have some promise but are costly and most effective on younger plants and require repeated treatments, which underscores the need for the first line of defense: prevention.

"Salvinia molesta could be the aquatic version of kudzu," said U.S. Fish & Wildlife Service biologist, Bob Pitman. "It’s like throwing a shroud over the water -- everything dies beneath it. Moreover, it’s easily and inadvertently spread by the aqua garden trade and by boaters."

Salvinia molesta is native only to Brazil. It’s become a world traveler and wherever it lands it creates problems. Farming and water-dependent economies in Australia and Africa have been decimated by infestations of this vegetative menace.

The U.S. Fish & Wildlife Service encourages hunters and fishermen to clean boats and trailers of mud and plants before leaving a boat ramp; outdoorsmen and women should look for this plant and immediately report any suspected sighting toll-free to the Aquatic Nuisance Species Hotline 1(877)STOP-ANS.

For additional information, contact Bob Pitman at 505/248-6471; bob_pitman@fws.gov.