LAKE BISTINEAU
LDWF'S FIGHT AGAINST GIANT SALVINIA:
RECENTLY UPDATED NEWS
*The following information is being updated as it becomes available. Please check back.
- October 20, 2009
Lake levels are still on the rise as a result of heavy rainfall during the last few weeks. Therefore, the drawdown to seven feet below pool stage is behind schedule. The goal of the drawdown is to strand the salvinia plants in the lake, but high water levels have allowed the plants to spread into areas that typically do not have water.
The increased rainfall has however caused the salvinia to move, and many acres once covered with giant salvinia have passed over the spillway or through the water control structure. Most of the plants are piling up behind the water control structure on Loggy Bayou Management Area.
Once the lake is down, department staff will further inspect the area. The information gathered will be used in developing a long-term plan for the lake. Efforts will focus on areas showing little response to the drawdown and potential causes for the lack of response. Many of these areas harbor salvinia and become nurseries for the plant.
Excavation and tree removal may be necessary in order lower water levels in these areas. If so, standard procedure will require us to obtain a U.S. Army Corps of Engineers permit. For those areas on private property, an executed agreement will be required.
Despite delaying the drawdown, the high water event does create a positive in this instance. The effects of the seven foot drawdown will be more significant than if the lake was at its normal stage.
We have yet to determine when the gates will be closed. Many factors will play into this decision. We are interested in doing some modifications to the spillway and lake bottom. Some of this work will require the lake bed to be bone dry. Other considerations include permits, MOUs, advertisement for bids, contracts, partnerships and funding. There is a possibility that the lake will be left down for another year or longer.
Mark McElroy
Fisheries Biologist
- September 28, 2009
The Department of Transportation and Development opened the gates on the Lake Bistineau water control structure to commence the 2009 drawdown of the lake. The lake level will be reduced by seven feet. However, recent rain events have kept the lake up, extending the amount of time required to reach minus seven feet.
This week, LDWF biologists will conduct an aerial assessment of the lake to determine a base line for giant salvinia coverage. In addition, they will evaluate the watersheds that contribute runoff to the lake to determine the extent of giant salvinia in the upper reaches. Lastly, they will take a look downstream of the dam. Several more aerial assessments are planned as the lake level lowers.
The purpose of the drawdown is to strand giant salvinia in the lake. Many have expressed concern that the water control structure does not create a situation where the plants can exit the lake. In this instance, it is not necessary. Salvinia is a fern, and if unable to access water, will dry out and die. Last year’s drawdown, along with foliar herbicide treatments, reduced giant salvinia coverage from 4,500 acres to about 850 acres.
At this time, there are no plans to close the gates. During the drawdown period, the department will evaluate the use of water fluctuation to facilitate plants to move from areas that will not drain. In order to do so, the gates may be closed; the lake will be allowed to fill to a certain level below pool stage and then opened after the plants move to stranding areas. The long-term plan to control giant salvinia in Lake Bistineau will place heavy emphasis on managing water level fluctuations.
The problems associated with Lake Bistineau extend far beyond the salvinia crisis. Many human activities have and continue to contribute to the degradation of the lake’s ecosystem. Over the past few weeks, we’ve spent a great deal of time developing a better understanding of water quality issues in the lake and watersheds. Our discoveries answer some very important questions as to why giant salvinia grows exponentially in this water body. There are many outdated, poorly maintained sewage treatment facilities throughout the watersheds that are responsible for a constant influx of nutrients. As a result, giant salvinia is being nourished, or fertilized in Lake Bistineau.
Sewage discharge is regulated by the Department of Environmental Quality and Department of Health and Hospitals as well as the parishes. Going forward, this issue must be addressed. This department will make the case with those government entities that have jurisdiction over this matter that non-compliance with state and local ordinances is contributing to lake degradation and ultimately giant salvinia growth. Addressing this situation will require routine monitoring of all sewage discharge, which in some instances will include maintenance or new installation.
Therefore, the rapid growth rate and resulting immense coverage of giant salvinia on Lake Bistineau can be directly linked to sewage discharge present in the water body.
Neglecting to address contributing factors will undoubtedly lead to less than desirable long-term results.
Mark McElroy
Fisheries Biologist
- September 10, 2009
Our friends at DOTD alerted us last week that they will require an additional week to finish their work behind the spillway. The structure is their responsibility, so we will wait patiently for this work to be completed and look forward to Wednesday, Sept. 16 to begin the drawdown.
Once the drawdown begins, our team will begin a new phase of investigating the issues that plague Lake Bistineau. Most of you who use the lake are aware that there are back water areas that don’t dewater with a 7 foot drawdown. Essentially, these areas are cut off from main channels and serve as nurseries for giant salvinia. This situation is unacceptable if we are to gain control of the plant. It will be vital for our team to evaluate these areas to understand what can be done.
The complexity of the terrain and sheer number of these areas will make reconnaissance difficult, especially in the upper reaches of the lake. While much of this work will be performed by ground crews, some of the work will be coordinated with aerial surveys. Large areas will receive the highest priority.
There is a still lot to be understood, and the answers seem to come in steps. Obviously, getting the water down is a giant step.
Mark McElroy
Fisheries Biologist
- What is giant salvinia?
Giant salvinia is a free-floating aquatic fern native to Brazil. It was brought into the U.S. by the aquarium and water garden industry.
A cluster of healthy giant salvinia.(Click photo to enlarge)
- How fast does giant salvinia grow?
This plant has the potential to double in biomass every 3-5 days. On Lake Bistineau, the plant is growing at a tremendous rate, doubling every week to 10 days during the prime growing season.
- When was giant salvinia first discovered in Lake Bistineau?
The invasive aquatic plant giant salvinia was discovered on Lake Bistineau in February of 2006.
Untreated, growing giant salvinia inhabiting shallow forested areas of Lake Bistineau.(Click photo to enlarge)
- How did giant salvinia get into Lake Bistineau?
Giant salvinia was likely transported to Lake Bistineau on one or more boat trailers sometime during the 2005 drawdown.
- Is this the only lake with this problem?
No. Giant salvinia has been found in nearly every public water body in northwest Louisiana and continues to spread to other areas of the state.
- Why can’t you simply spray it and kill all of it?
Giant salvinia is very difficult to control with foliar herbicide applications because the leaves have specialized hairs that are very efficient at keeping water off the leaf making it very difficult for herbicides to be absorbed by the plant.
LDWF personnel spraying an herbicide treatment on giant salvinia growing along a developed shoreline.(Click photo to enlarge)
- Why don’t you spray it from the air?
LDWF has a contract for aerial herbicide applications but there is a fairly long lead-time in letting the contract and arranging for an application to be made. At times, large mats of giant salvinia can be found in open water areas of the lake that would be suitable for aerial applications. However, when the wind changes the salvinia is blown to other areas of the lake where the cypress canopy or adjacent inhabited shorelines do not allow for aerial applications.
- Why don’t you put grass carp in the lake and let them eat it all of it?
Giant salvinia is not considered a preferred diet choice for grass carp.
- Did last year’s drawdown do any good? The lake is just as bad now as it was last summer in front of my house.
There were approximately 4,500 acres of giant salvinia on Lake Bistineau prior to the July 15, 2008, start of the drawdown. In conjunction with ongoing herbicide applications, dewatering the lake and allowing the giant salvinia to dry and desiccate had reduced the salvinia to approximately 850 acres in mid-March of 2009. This reduction in acreage was short-lived as heavy rains and a resulting rise in lake level beginning in May 2009, flushed large quantities of salvinia down to the lower end of the lake. With warming temperatures the salvinia began growing very prolifically, causing problems in these areas including boating and fishing access and aesthetics issues for shoreline property owners.
Giant salvinia that is dying following an herbicide spray treatment.(Click photo to enlarge)
- Why don’t you just drain the lake and leave it down for a couple of years?
With the drawdown structure that is currently in place, the maximum drawdown capability of Lake Bistineau is seven feet below normal pool stage. A drawdown to this level reduces the surface acreage at pool stage by approximately half. Giant salvinia continues to grow in the remaining water, much of which is extremely difficult to access by boat for herbicide applications. Lake Bistineau also has a very large watershed and is not likely to remain in a drawdown condition during rainy periods.
- Why don’t you figure out some beneficial use for giant salvinia so people will want to extract it out of the lake?
Currently, there is no known use for giant salvinia that is economically feasible.
- What about the weevils (bugs) that are supposed to eat the giant salvinia?
Salvinia weevils were introduced into two enclosures on the lake in August of 2007. The weevils survived their first winter and their populations increased in the enclosures. Additional weevil infested salvinia was stocked in Lake Bistineau in October of 2008 from nursery ponds near Gheens. A major weevil stocking effort in Lake Bistineau began on June 15, 2009. During the two-week stocking effort, over 78,000 lbs. of giant salvinia infested with over 1.8 million adult weevils was relocated from LSU’s rearing facility located near Gheens to Lake Bistineau.
Giant salvinia weevils may serve as a biological control tool in Lake Bistineau.(Click photo to enlarge) An Enclosure containing weevil infested giant salvinia.(Click photo to enlarge)
- Will the spray hurt the weevils?
The areas where the weevils have been stocked are not targeted for herbicide applications. The goal is to allow the weevils to reproduce and spread throughout the lake.
A cluster of giant salvinia with an adult weevil.(Click photo to enlarge)
- Is it safe to use the lake water for irrigation purposes?
Some of the herbicides being used by LDWF spray crews or private contractors have water-use restrictions. Diquat, which is used in some of the foliar herbicide applications, has a 5-day restriction for irrigation purposes. Water treated with Galleon herbicide can be used for irrigation of turf grass at levels under 30 PPB but should not be used to water food crops (vegetable gardens) or ornamentals at levels in excess of 1 PPB. It depends on where on the lake your water intake is located and when herbicide applications have been made in the area. Please contact the District 1 Office for more information at 318-371-3050.
- Why don’t you use a mechanical harvester like the ones they have in Texas?
Mechanical harvest and removal of giant salvinia is very expensive and labor intensive. Even the best harvesters can only harvest a couple of acres a day.
- Why would the department not consider using salt to treat giant salvinia in Lake Bistineau?
Salt will indeed kill giant salvinia at 10 ppt. However, salt will kill bald cypress at 3 - 4 ppt. To obtain 10 ppt saltwater in Lake Bistineau it would take 4,186,663,988 pounds of salt. Therefore, salt is not a reasonable solution. - Why were the Galleon herbicide treatments curtailed in Lake Bistineau?
Galleon was used to treat giant salvinia at seven sites on an experimental basis. Tests revealed that Galleon rapidly diffused away from six of the seven sites and was essentially ineffective at those sites. Based on theses test results, and in consideration of the approaching drawdown, Galleon treatments were curtailed. Galleon treatments may be considered for use in some locations during the drawdown.
- Will Lake Bistineau be closed to recreational fishing activities during the drawdown?
No, these activities do not negatively impact the resources there.
For more information, contact: James M. Seales II, District 1 Fisheries Biologist Manager at (318) 371-3063 or jseales@wlf.la.gov.
News Releases
2009 News Releases
- 09/22/2009 - LAKE BISTINEAU DRAWDOWN INITIATED ON SEPT. 16
- 06/22/2009 - L.D.W.F. AQUATIC PLANT CONTROL PROGRAM INCREASING SALVINIA WEEVIL POPULATION ON LAKE BISTINEAU
2008 News Releases
- 10/21/2008 - L.D.W.F. INTRODUCES WEEVILS TO COMBAT AQUATIC WEEDS
- 06/03/2008 - LAKE BISTINEAU DRAWDOWN TO BEGIN JULY 15
- 05/14/2008 - L.D.W.F. AQUATIC PLANT CONTROL PROGRAM COMPLETES SECOND WEEK-LONG HERBICIDE APPLICATION AT LAKE BISTINEAU
- 04/15/2008 - L.D.W.F. AQUATIC PLANT CONTROL PROGRAM MAKES PROGRESS AT LAKE BISTINEAU
- 04/10/2008 - L.D.W.F. AQUATIC PLANT CONTROL PROGRAM TARGETING LAKE BISTINEAU
Maps
The 17,200-acre lake just south of Doyline is a popular fishing spot for bass and crappie with private dwellings and Lake Bistineau State Park offering lakeside accommodations.
 | Statewide Salvinia Distribution Map |
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