Killer Weed

The life-suffocating Salvinia molesta has entered Texas waterways. It's green, fast and deadly.

Helton and Hartmann, working out of a tiny portable building deep in the East Texas woods, are on the front lines of the battle against molesta. "It's just eating our lunch," Helton says.

Molesta will never completely cover any of Texas's large lakes, but it can easily take over the coves and byways that dot the shorelines of those reservoirs. Those are the prime fishing areas and the spots where expensive lakeside homes are built. After Giant Salvinia enjoys a prime growing season, those fishermen and homeowners might find a rude shock when they see their favorite water spots covered with a thick, green vegetative mat.

Molesta is much more aggressive than hydrilla, a somewhat similar plant that has also caused problems in Texas. In one of the several private-pond Giant Salvinia infestations authorities dealt with since the discovery at Browning Elementary, the molesta growth was so thick that ducks nailed mid-flight by hunters had landed with a dull thud on the vegetation, unable to pierce through to the water. ("When this plant really gets going, you can roll a golf ball across it and it'll never get wet," Hartmann says.) And unlike hydrilla, which bass fishermen like because it attracts their quarry, Giant Salvinia has no redeeming features for sportsmen.

Perhaps more financially ominous than spoiling fishing sweet spots or lakeside views is the threat of what might occur if molesta makes its way past the dams that create Texas's lakes. Galveston Bay is safe -- the plant can't survive salt water -- but the water systems of Toledo Bend and Rayburn, and other lakes, are used to irrigate the rice fields that are a backbone of the local agricultural economy.

"You could get one piece that gets by the screen [of the irrigation system] or gets on a turtle's back or the legs of a waterfowl, and you'd get this in the rice fields," Helton says. "It's scary."

With doomsday scenarios aplenty, local and federal authorities have created a Giant Salvinia Task Force, featuring the resources of such groups as Texas's and Louisiana's wildlife authorities, the National Park Service, U.S. Geological Survey and Department of Agriculture, the U.S. Army Corps of Engineers and Texas A&M and Florida A&M universities. The task force met in September at the Ramada Inn at Bush Intercontinental Airport to begin mapping out a strategy to take on the unprecedented challenge.

They've heard the horror stories from Australia, where all manner of eradication methods have been used without success. They're hoping that by catching the phenomenon early, they will be able to control it before it gets to be the problem it has become in other places.

Typically, there are three main ways to deal with aquatic infestation of so-called exotic nuisances: mechanically, biologically and chemically. Put simply, you see if you can pull the plant from the water and hope you get it all; you find a bug that will eat it; or as a last resort you use herbicides.

Molesta will never be contained merely by mechanical means, officials are sure. The plant reproduces too fast, and such machines are too expensive, to make the effort feasible. Officials can also "draw down" the level of lakes by a couple of feet, stranding the plant on the shore and letting it wither away, but that isn't likely to kill enough of the weed, either.

The biological option offers slightly higher hopes. The Salvinia weevil is in regular use in Florida, where it's used to battle Salvinia minima, a more common and less aggressive form of Giant Salvinia. The tiny bug eats nothing but salvinia plants, scientists say, meaning it won't destroy desirable vegetation. Plans are underway to collect the bug -- a labor-intensive, not inexpensive job -- and get the necessary permits to transport it across state lines next spring.

"We're hopeful this insect will provide a lot of assistance in getting rid of the plant; it can get into places where the water is too remote or shallow for us to get in there," Helton says. "It's shown real promise, but I don't want to give out any false hopes. I've never seen any biological control that can be the whole answer."

"It's just one tool in the tool box," says Hartmann, noting that molesta growth rates can outpace the bug's consumption rates. The bug is more of a crawler than a flier, too, and requires all but being placed on the plants for a population to take hold.

That leaves the third option, herbicides, and that option is the touchiest one of all. The Texas Parks & Wildlife Department has plenty of critics who charge the agency is all too eager to use chemicals in its fights against various nuisance plants.

"I get real worried when they reach for the herbicides," says Sue Pittman, a network coordinator for the Chemical Connection, a statewide group that monitors the TP&WD. "They should be thinking about mechanical means; if this plant is not attached to the bottom of the lake, they should get a big sucker-upper and just suck it up. It doesn't make sense to use chemicals."

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