COLLEGE STATION — A fern that has clogged waterways on at least four continents has been identified in Texas, and scientists fear that the weed might already have gone beyond control levels.
Giant salvinia, which is capable of doubling in less than a week, has been found in the Toledo Bend Reservoir bordering Louisiana, Cow Bayou in Orange County and in parts of Harris County near Houston, according to Dr. Michael Masser, Texas Agricultural Extension Service fisheries specialist. Samples also are being identified from Fort Bend and Galveston counties to determine if the plant has spread there.
“The problem is that when this plant gets started, with its phenomenal growth rates, it covers the surface of a body of water,” Masser said. “On the surface, it looks like a little thing with each leaf about the size of a thumbnail. And it forms roots under the water and floats, reproducing vegetatively along the way.”
Not only does Giant salvinia spread horizontally to cover the surface of water, but it continues to grow vertically on top of itself as well, often forming mats over time that may be 2-feet deep, Masser said.
“In covering the surface, any native plants are shaded out and die,” Masser said. “And the death and decomposition of those plants depletes the oxygen in the water and kills the fish.”
Research on other continents where the plant, known scientifically as Salvinia molesta and commonly as Kariba weed, has shown that it can harbor diseases and is a breeding ground for disease-carrying insects.
“Realistically, when you look at a 185,000-acre lake (Toledo Bend) and a plant that floats and moves with the wind, I think we’ll only be able to maintain it at the lowest feasible level,” said Rhandy Helton, Texas Parks and Wildlife agent in Jasper.
Masser and Helton are part of a federal-state special task force that has been set up in hopes of eradicating from Texas the new weed, classified as one of the most dangerous and hard to control water plants in the world. Helton noted that Giant salvinia is the new weed identified, but all salvinias there are about 10 species — are prohibited in the state.
Part of the problem, however, is that most people don’t realize that the water fern, which is quite attractive as an individual plant, is a noxious, prohibited weed. In fact, a quick search on the Web found several suppliers ready to package the plant and ship it anywhere in the world. One site even noted for potential buyers that salvinia “grows like a weed.” A large clump of the plant can be had for $5.
“We really are concerned that it is being spread through the water garden and the aquatic plant industry,” Masser said. “That probably is how it got into this country with imported aquatic plants. It is against federal law to spread it across state lines and in Texas all salvinias are illegal to possess.”
Masser said a supplier was found in Wichita Falls and his plants traced to a Dallas supplier, but neither knew of the law.
“We don’t want to fine anyone, we just want to get rid of it,” he said. “So, we are trying to educate people about it.”
Now that the plant is known to be growing in several bodies of water, experts said, it is likely to spread on boats and other water equipment as well as by floating through creeks and streams.
“We’ll be looking at biological, chemical and manual means of eradicating this weed,” Masser said.
Helton added that the task force already is preparing paperwork to allow an effective salvinia weevil to be brought to Texas from Florida to chomp away at the weed.
The task force asks that anyone who thinks the weed is present in waterways to contact state or federal officials. A picture of Giant salvinia is on the Web at <http://www.toledo-bend.com/alliance/docs/salvinia.html>. Helton can be reached at (409) 384- 9965, or toll-free at (800) 792-1112. Masser is available at (979) 845-7370,m-masser@tamu.edu. There also is an e-mail address to report possible sightings atsalvinia@sra.dst.tx.us
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