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to control Ludwigia in Russian River, Laguna By CAROL BENFELL THE PRESS DEMOCRAT The worst infestations of Ludwigia are in the laguna near Sebastopol and in flood-control channels in Rohnert Park, where the weed now sprouts five feet above the water. The plant smothers native plants and makes it harder for waterfowl to land on the water surface and find food. It decays in the water, depleting oxygen and killing fish. Now research shows the weed is changing the waterways in which it lives, creating an environment favorable to the specific kinds of mosquitoes that carry West Nile virus, which can sicken or kill birds, horses and people. Researchers think Ludwigia entered the laguna when someone dumped an aquarium containing the plant. West county Supervisor Mike Reilly last week called on the government agencies with control of the laguna to step up their research on ways to reduce the threat to human health. ``It only makes sense from a public health standpoint to be proactive about this,'' he said. ``We're seeing West Nile in birds, we're seeing it in horses, and I think it's just a matter of time'' until it appears in people. He said he has asked the Laguna Task Force, a coalition of government agencies with responsibility for the laguna, to give him a plan and options for Ludwigia control by Oct. 20. But bringing Ludwigia under control is not going to be easy, researchers say. The plant reproduces from every broken-off section of root, leaf or stem and produces hundreds of seeds as well. ``This thing is a real menace,'' said Donald Strong, who specializes in the study of invasive aquatic plants at UC Davis. ``With enough money and enough attention, you could probably eradicate it -- I guess.'' Ludwigia is a problem because it forms dense mats and towering columns that protect juvenile mosquitoes from natural predators. It interferes with the mosquito control district's efforts to disburse mosquito larva-killing pellets. But it's worse than that -- its roots slow the flow of water and increase the buildup of silt, creating a stagnant, foul pool that's the prime habitat of the Culex pipiens mosquito, a prime carrier of West Nile virus, said Anna Sears, director of research for the nonprofit Laguna Foundation, an environmental group. Ludwigia's leaves cover and smother native plants and decrease the amount of open water where ducks can land and herons can wade in search of food, Sears said. Its decomposing leaves rob the water of oxygen, leading to fish die-offs, she said. ``Whenever you get a strongly invasive species like this dominating an area, you can have a really substantial impact on the whole ecological system, affecting plant and animal communities,'' Sears said. |
The foundation, working with state and local agencies, has begun its own research effort with the help of Lily Verdone, a graduate student from Sonoma State University.
You can reach Staff Writer Carol Benfell at 521-5259 or cbenfell@pressdemocrat.com. |
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LUDWIGIA HEXAPETALA FACTS |
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