News and Activities
Weed Control Strategy for Giant Salvinia
Date Posted: April 28, 2000
Giant salvinia, Salvinia molesta, a floating aquatic fern from Brazil, is an aggressive colonizer of slow/still waters - capable of doubling its population size in 2-3 days, ultimately forming mats over 2 feet thick. Salvinia was introduced to the United States for the aquarium and ornamental pond trade. It was first observed in the U.S. in 1997 at a school yard demonstration pond in Houston, TX. The plant is easily transported and can become established in suitable aquatic sites merely by flushing the plant down the toilet. The plant is also moved from site to site through boats, outboard motors, boat trailers, and other water-borne recreational equipment. Giant salvinia has been observed on the lower Colorado River in California and Arizona. It is now present in California, Arizona, Texas, Louisiana, Mississippi, Alabama, Florida, and Hawaii. The plant has been especially problematic in Texas and Florida, choking waterways, lakes and ponds, and is now on the Federal List of Noxious Weeds. Service Refuges and Division of Environmental Contaminants staff are working with federal, state, and local officials to develop an integrated weed strategy for Giant salvinia that also provides protection for threatened and endangered species. In Region 1 (California, Idaho, Nevada, Oregon, Washington, Hawaii and the Pacific Islands), the Service is working with the California Dept. Food and Agriculture to control giant salvinia along the Palo Verde Drain and Irrigation System, California (near the Colorado River) using integrated weed management. Mechanical and physical control methods (fine mesh nets and drag-line buckets) as well as herbicide treatment will be used. Biological control of giant salvinia is provided by larvae and adult weevil, Cyrtobagous salviniae, but this weevil is not yet approved for release by the California Dept. Food and Agriculture. The weevil larvae feed inside the rhizomes, and the adults feed on bud growth.
Scott M. Stenquist, 503-231-6172