Giant salvinia is considered the most noxious aquatic plant species in the country. Giant Salvinia, Salvinia molesta was identified in the marshes and canals just north of the town of Cameron in the late fall of 2001. This is only the second confirmed finding of giant salvinia in Louisiana after being found several years ago in Toledo Bend. Its smaller cousin the Common Salvinia, Salvinia minima has been growing unchecked in coastal Louisiana since the early 1980’s.
Giant salvinia is much more damaging than its smaller cousin because of its ability to grow into dense mats that can cover entire water bodies with a thick layer of vegetation. These mats smother native plants by blocking the penetration of sunlight into the water. Other consequences of giant salvinia are reduced dissolved oxygen causing fish kills and reduced production of submerged aquatic plants due to shading. This severely reduces the value of an area for waterfowl habitat. Solid mats of giant salvinia may also reduce or eliminate boating and fishing opportunities simply because boats are not able to push through the thick mats. These mats could clog drainage canals causing widespread flooding damage. They may also have devastating impacts on rice production by clogging canals used as surface water irrigation sources. Potential impacts of giant salvinia in rice production fields could also be devastating. It could also adversely impact crawfish and catfish production.
LSU AgCenter Actions
Media Day: TV, newspaper, and radio reporters came to Cameron from all over the state to cover the infestation. There was statewide media coverage reaching thousands of people. Numerous phone calls and contacts proved the effectiveness of this program and that public awareness was prominent.
Stakeholders Meetings (2): Local government, drainage board, landowners, cattle producers. Two meetings were held to discuss plans for control. 50 people learned about the infestation and control options.
Salvinia Workshop: Attended by 50 local landowners, drainage board employees (Cameron &Calcasieu) Participants learned: to identify giant salvinia, work being done, and control options.
Giant Salvinia Powerpoint: 10 public speaking engagements educated civic clubs, drainage boards, economic development groups, college classes about giant salvinia and the threat it poses.
Cyrtobagous Weevil Release: Weevil release and control sites were established and monitored. Additional releases are planned for August 2002.
Reward Spray Demonstrations: Herbicide demonstration plots were shown to be effectively controlled when Reward was applied using ground rigs (tractor, boat). Ground rigs are a cheaper, more effective alternative to aerial application due to the improved coverage rates and volume of application.
Rodeo herbicide Research: Herbicide trials were carried out using Rodeo, a cheaper, less restrictive alternative to Reward. Preliminary results look promising.
Salinity Tolerance Study: The tolerance threshold of giant salvinia was found to be at 10 parts per thousand (28% seawater strength) for 5 – 7 days. Salinity is a cheap, effective control method when applicable.
Aquatic Weed Control Funding: LSU AgCenter worked closely with Louisiana Department of Wildlife and Fisheries and state legislators to secure funds to control giant salvinia and other aquatic weeds through a bill passed by legislators which would increase fees on light duty trailers. Dr. Dearl Sanders testified before the senate committee sponsoring the bill. A portion of the funds raised will be dedicated to LSU Agcenter aquatic weeds research.
Current Situation/Results
Less than 10% of the original volume of giant salvinia found in the fall of 2001 existed as of July 1, 2002. Two “Reward” applications, an extensive drawdown, followed by the introduction of saltwater yielded good control. However, abundant rainfall in the month of July, 2002 has increased growth and helped the spread of giant salvinia. The general public in addition to direct stakeholders are highly aware of the threat of giant salvinia as evidenced by the numerous phone calls and plant samples brought in for identification and control recommendations.
