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Jan. 16, 2007
Volunteers Set Precedent To Control Invasive Exotic Plant
JASPER, Texas—Message from residents of Karnack, Texas, to giant salvinia: Don’t mess with our lake!
When Howard Elder, aquatic vegetation biologist for the Texas Parks and Wildlife Department, needed help fighting an infestation of the invasive aquatic plant giant salvinia in Caddo Lake, residents of the tiny East Texas community quickly volunteered.
In December 2006, 35 citizens received training in how to recognize and dispose of giant salvinia and were issued permits allowing them to do so.
“It is illegal to possess or transport giant salvinia without a permit, but these people wanted to do something to help protect their lake,” Elder said. “Involving them as permitted volunteers gives them ownership of the management of the water they live near.”
Caddo Lake residents have even drafted a “Community Response Plan” which outlines specific goals and objectives to help coordinate volunteer efforts. In addition to creating a “Shoreline Watch” program which will provide quick and decisive control of new infestations, the plan involves actively researching new sources of funding for control efforts.
Elder is planning another training session in the spring. In the meantime signs will be placed around the lake warning people of giant salvinia’s presence and steps they can take to help prevent its expansion.
“The signs will help people identify giant salvinia and encourage them to inspect and clean boats and trailers before leaving launch areas,” Elder said.
Giant salvinia is an invasive floating aquatic fern from Brazil. According to Dr. Earl Chilton, TPWD aquatic habitat enhancement program director, giant salvinia is one of the world’s most invasive aquatic weeds.
“It has caused problems in Australia, New Guinea, New Zealand, Rhodesia, and Sri Lanka to name a few,” Chilton said.
Under ideal conditions, giant salvinia populations can double every 5-to-8 days, are resistant to cold weather, and can survive for weeks out of water if kept moist. Once established, the fern forms dense mats that eliminate all other aquatic vegetation in the area, even plankton, which are vital to healthy fish populations.
Juvenile plants, spread by wind and wave action, quickly start new colonies in protected backwaters. Giant salvinia is easily spread overland to new locations by boat trailers, propellers or jet-ski intakes; most new infestations are found near boat ramps.
More than 150 acres of the invasive fern were discovered in Caddo Lake in May 2006 in Jeem’s Bayou, Louisiana. Subsequent surveys revealed almost 300 acres of giant salvinia in the area. Louisiana vegetation control crews, with the assistance of TPWD, responded with aggressive chemical treatments in an effort to prevent uncontrolled expansion of the exotic.
Since its arrival in Texas waters in 1998, giant salvinia has been documented in Toledo Bend Reservoir, Lake Conroe, Sheldon Lake, and Lake Texana. In 2006 giant salvinia was confirmed on Caddo Lake, Center City Lake and Lake Pinkston in East Texas. Although many infestations are never reported, giant salvinia persists in at least 50 private water bodies in Texas.
An integrated pest management program combining public awareness and education, chemical treatment, physical removal and introduction of bio-control agents like the giant salvinia weevil (Cyrtobagous salviniae) is considered to be the best long-term management approach.
Although aquatic herbicides remain the first line of defense in controlling new infestations, the introduction of salvinia weevils as a bio-control agent has shown great promise on Toledo Bend Reservoir and Lake Conroe. Elder is also stepping up efforts to introduce weevils on the Louisiana side of the lake in cooperation with Louisiana authorities.
“We have a high density of giant salvinia weevils in at least two places on Toledo Bend Reservoir that need to be harvested and distributed to locations where they will do the most good,” Elder said.
Public involvement and awareness are critical in identifying and controlling new infestations and are considered a priority in control efforts. Anglers and boaters can help by learning to identify giant salvinia and reporting any suspicious floating aquatic vegetation, particularly around boat ramps and the backs of nearby creeks.
Boats, trailers, jet-ski intakes, and other equipment should be inspected frequently and cleaned of all aquatic vegetation before leaving launch areas.
For information on giant salvinia in East Texas, to report possible sightings or to inquire about future volunteer training sessions, call Howard Elder, Aquatic Habitat Biologist, 409-384-9965, firstname.lastname@example.org, or Tim Bister, Fisheries Biologist District 3-A, 903-938-1007, email@example.com.
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