Experts Agree: Comprehensive Control Plan is Needed for Management and Eradication of Giant Salvinia


WASHINGTON, D.C., June 27, 2011 - Today, the House Subcommittee on Fisheries, Wildlife, Oceans and Insular Affairs held a field hearing in Shreveport, Louisiana titled “Giant Salvinia: How Do We Protect Our Ecosystems?” Subcommittee Chairman John Fleming (LA-04) and Representative Louie Gohmert (TX-01) attended the hearing and heard from Administration, state and local experts on the status of the fight against giant salvinia, what control or eradication methods have worked and at what costs, and ways by which these efforts can be financed in the future.

“The fight to eradicate giant salvinia will be a long and arduous battle. Once an invasive species has become established it is difficult, if not impossible, to completely remove it. There is no silver bullet to kill giant salvinia. What we know, however, is that its biomass can double in size in a week or ten days and that its expanded mats of vegetation degrade fishing habitats, decreases water quality, creates unsafe boating and fishing access and threatens property values. We will continue to contain this invasive species by utilizing a number of different strategies including simple things like making absolutely sure that once a boat is removed from a lake, the boat owner does not allow giant salvinia to hitchhike home,” said Chairman Fleming (LA-04).

“Giant salvinia is a reminder of just how devastating an invasive species can be if left untreated. Just a small plant, innocent in appearance, salvinia can completely take over and destroy the ecological and recreational environment of a lake. We have not made significant strides in dealing with this innocuous-looking lake killer. But, when a floating aquatic plant growing on a freshwater lake can choke out all life underneath its spreading mass, and we rely on those lakes for our freshwater, then we have a critical problem. When one boat trailer can come out of an infected lake with a two-inch plant, then back it into another lake two weeks later, and that small plant becomes hundreds or thousands of acres of lake-choking mass within months, it is a problem we must solve,” said Rep. Louie Gohmert (TX-01).

Louisiana State Representative Henry Burns also attended the hearing, noting: “What is at stake? Quality of life, recreational opportunities, property values and economic development. Without question, it will take a team effort just to manage this problem.”

Giant salvinia is a free-flowing, rootless aquatic invasive fern, which floats just below the water surface, is native to south-eastern Brazil and was legally imported into the United States to be used in aquariums and garden ponds. It has been declared one of the world’s worst weeds due to its prolific growth rates, effective means of distribution, and difficulty of control. Since 1995, giant salvinia has been discovered at 90 different locations in 12 states including Alabama, Arizona, California, Florida, Georgia, Hawaii, Louisiana, Mississippi, North Carolina, South Carolina, Texas and Virginia.

Giant salvinia first appeared in Louisiana in 1998 when a handful of plants were collected at Bayou Teche. A single plant has been found to cover 40 square miles in three months. By forming huge mats of vegetation, this aquatic weed creates “dead zones” in freshwater ponds and lakes by blocking out the sun’s rays from penetrating through the water column thereby inhibiting photosynthesis and killing everything below it. In addition, it degrades fisheries habitats, decreases water quality, creates unsafe fishing and boating access, and threatens the property values of lake front communities.

Witnesses at the hearing spoke of management methods that have been used to control and eliminate giant salvinia. These methods include chemical control, biological control, flushing and drawdowns. Michael J. Grodowitz, Research Entomologist for the Army Corps of Engineers, discussed the benefits and drawbacks of each control method. According to Grodowitz, chemical control is effective and the most prevalent control method in the United States, but tends “to produce only short-term control and can become expensive, especially when multiple treatments are needed over the course of a growing season.”

Robert Barham, Secretary of the Louisiana Department of Wildlife and Fisheries, highlighted the exorbitant cost of chemical control: “For each gallon of Galleon, the herbicide our Department utilizes, it costs us $1,851 per gallon. With more than 25,000 acres infested, simply spraying would be an incredibly expensive and likely ineffective task. And the costs not included in the cost per gallon for herbicide are the manpower costs to the state, the cost of the equipment, the boats and the fuel.” The salvinia weevil, a natural predator of giant salvina, is the method of choice for many infestations overseas for biological control, yet can take several years and is sensitive to cold weather. Flushing and drawdowns also have their share of disadvantages which include increasing the distribution of salvinia downstream and scattering remaining plants throughout the water body making treatment even more difficult.

Experts agree that a comprehensive control plan needs to be developed in order to successfully control and eradicate giant salvinia. Michael Massimi, Invasive Species Coordinator for Barataria-Terrebonne National Estuary Program, believes a successful control plan should “include significantly increasing the number of weevils to be released, incorporating technology such as satellite imagery and software development to inform monitoring programs, developing new funding strategies, and coordinating collaborative control that can strategically integrate weevil release zones with chemical spray zones and other control efforts.” He also emphasized the need for education and outreach.

Kenneth Lynn Ward, Project Manager for the Parish of Caddo, Louisiana, spoke of the economic toll giant salvinia infestation takes on local communities and the costs associated with control efforts. “The loss of historic Caddo Lake due to giant salvinia would be the loss of a way of life to our Parish. Jobs that derive from the lake would be lost. Families would have to move away from Caddo Lake to find work. Recreational opportunities would be lost, and high quality drinking water would be lost. The Parish of Caddo has spent more than $40,000, not to mention the State funds that have been spent, to save this valuable resource.” Robert Barham, whose office is charged with battling giant salvinia, utilizes a $6.9 million invasive aquatic species budget for control efforts.

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Contact: Jill Strait, Spencer Pederson or Crystal Feldman 202-226-9019

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