LOUISIANA DEPARTMENT OF
WILDLIFE AND FISHERIES
OFFICE OF FISHERIES
INLAND FISHERIES SECTION
2020 AQUATIC VEGETATION CONTROL PLAN
SALINE LARTO COMPLEX
Located in Rapides, LaSalle, Avoyelles, and Catahoula Parishes
Map in Appendix 1
1. Waterbody type – Impounded natural backwater system
2. Age and condition of control structure – The original Larto structure was built in 1958.
The current structure was completed in 1997. As per the August 10, 2010 Louisiana
Department of Transportation and Development (DOTD) Dam Inspection and Evaluation
Report, the Larto Lake Dam appears to be in fair maintenance condition fulfilling its
intended purpose.
3. Type of control structure - The concrete structure consists of a 257- foot wide spillway
with a drawdown gate and 4 flapper gates. The drawdown gate is a vertical slide gate
with an opening that is 9 feet wide and 11 feet tall. The 4 one-way flapper gates are 4 feet
high by 7 feet wide. The flapper gates are designed to restrict the inflow of turbid Red
River water up to 42’ MSL, while allowing Larto Lake water above 37’ MSL to drain out
of the lake. (See Appendix II)
4. Water level (MSL) – Pool Stage – 37’
5. Surface area – 8,000 acres at pool stage
6. Average depth – 8’ at pool stage
7. Watershed ratio – 12.5:1
8. Drawdown potential of structure – 5.5’ maximum drawdown at an approximate rate of 1
inch per day.
9. Waterbody Board or Lake Commission – The Catahoula Parish Police Jury (CPPJ) is the
lake authority. The Larto Lake Game and Fish Preserve was abolished by Act 1262 of
1995. Personal communication with the CPPJ indicated that no current lake commission
has been appointed.
a. Creation / Nomination – N/A
b. Primary contact information – Catahoula Parish Police Jury
P.O. Box 258
Harrisonburg, LA. 71340
318-744-5435
c. Procedure for spillway openings – Drawdowns recommended by the Louisiana
Department of Wildlife and Fisheries (LDWF) for lake management purposes will
be presented to the CPPJ prior to being enacted. As outlined in Louisiana
Legislative Act 270 of 1984, gate opening will be coordinated between the
Louisiana Department of Transportation and Development (DOTD) and the
LDWF.
What significant stakeholders use the lake?
The lake is used for agriculture irrigation, fishing, duck hunting, and water recreation.
There are many homes and camps located along the shoreline.
10. What is the history of aquatic vegetation complaints?
The amount of vegetation varies substantially from year to year depending on water level
fluctuations. Minimal complaints about hydrilla (Hydrilla verticillata), American lotus
(Nelumbo lutea), alligator weed (Alternanthera philoxeroides), water primrose (Ludwigia
spp.), and common salvinia (Salvinia minima) arise following several years without a
high water event. The recent discovery and spread of giant salvinia (Salvinia molesta) has
increased vegetation complaints considerably.
11. Have there been any controversial issues on the lake?
Cross Bayou weir, Denny’s Drain weir, and Open Mouth Bayou weir have been
susceptible to structure failure (blow outs) during high rainfall periods.
The Cross Bayou weir water control structure had a significant washout following a high
water period. Department personnel confirmed the washout on January 28, 2013. The
washout was 75 feet wide and 6 feet deep. The temporary repair was completed on
February 10, 2013. The lake water level returned to normal pool elevation on February
12, 2013. Permanent repairs to the Cross Bayou weir were completed in 2014.
Aquatic Vegetation Status:
A survey was conducted on December 2013. No serious vegetation problems were observed.
A number of emergent species were present including alligator weed, American lotus, water
pennywort (Hydrocotyle spp.), water primrose, and water hyacinth (Pontederia crassipes).
This vegetation was sporadic and scattered throughout the complex. Total acreage for all
species combined was less than 500 acres. Submersed vegetation was minimal. Common
DRAWDOWN HISTORY
Gates Opened
Gates Closed
Purpose
Results
Issues
1982 Turbidity Temporary
Water clear till Red River
water returned
1983
Turbidity
Temporary
Water clear till Red River
water returned
1984
Turbidity
Temporary
Water clear till Red River
water returned
1985
Turbidity
Temporary
Water clear till Red River
water returned
July 10, 2014
Sept. 24, 2014
Returned to
pool 1-4-15
Repair CBW Good Very slow rate of fall
Note: Unintentional dewaterings occurred in 1985, 2008, and 2013 due to weir blowouts.
salvinia was scattered throughout Shad Lake, but no mats were observed, totaling less than
100 acres. On October 30, 2012, giant salvinia was discovered at the Open Bayou boat ramp.
An intense survey of the immediate vicinity was conducted, and no additional giant salvinia
was located. The giant salvinia found covered less than an acre, and it appeared to be
confined to Open Bayou. Department spray crews treated the area repeatedly over the next
few months to prevent giant salvinia from spreading. All floating and emergent vegetation in
the vicinity that could have harbored salvinia was treated.
A vegetation survey was conducted on the Saline-Larto Lake complex on March 18, 2014.
There were no vegetation problems at that time. Total coverage for emergent and submersed
vegetation combined was less than 100 acres. No late summer or fall vegetation survey was
conducted. The lake water level was lowered for the construction of the Cross Bayou Weir.
As of December 16, 2014, the Saline-Larto Lake complex water level remained
approximately 3.5 feet low. The lake returned to pool elevation on January 4, 2015. Water
hyacinth had been observed in several areas, but was not expected to exceed 300 acres of
coverage in 2015.
A vegetation survey was conducted in June 2016. There was very little submersed
vegetation. The submersed vegetation observed was hydrilla, coontail (Ceratophyllum
demersum), and fanwort (Cabomba caroliniana). There were approximately 50 acres total.
The emergent vegetation present was American lotus, alligator weed and water primrose. The
most prevalent emergent plant was American lotus, mainly in Shad Lake. There were
approximately 400 acres of emergent vegetation total. Floating vegetation observed was
common salvinia, water hyacinth and duckweed (Lemna minor). There were approximately
400 acres of floating vegetation present. In October of 2016, Giant Salvinia was discovered
again in Open Bayou/ Little Saline area. Since the discovery, a high water event flushed the
salvinia out and spread the vegetation into the coves of Saline Lake.
A vegetation survey was conducted on July 19
th
, 25
th
and August 1st of 2017. There was very
little submersed vegetation observed. The submersed vegetation present was hydrilla,
coontail, fanwort and bladderwort (Utricularia spp.). There was approximately 150 acres of
submersed vegetation. Emergent vegetation present was American lotus, primrose, and
alligator weed. The majority of the lotus was located on the fringes of various bayous and in
the Saline Lake area. Shad lake, which typically has large amounts of lotus, had very little at
that time. There were approximately 800 acres of American lotus present. Primrose and
alligator weed were present on the fringes of various bayous and lakes. There were
approximately 100 acres of primrose and alligator weed combined. The major floating
plants observed were common salvinia and giant salvinia. Common salvinia was observed
sporadically throughout the complex. The majority of the common salvinia was observed in
the Shad Lake area, and covered a total of approximately 400 acres. Giant salvinia was
observed in Big Creek, Little Saline, Saline Lake and all connecting bayous of Little Saline
and Saline Lake. No giant salvinia was observed east of Saline Lake. There were
approximately 800 acres of giant salvinia present.
A vegetation survey was conducted on July 26 and July 30, 2018. There was less than an
acre of submersed vegetation observed. This consisted of coontail and hydrilla. Emergent
vegetation observed was approximately 140 acres of alligator weed, 30 acres of water
primrose, and 140 acres of American lotus. Floating plants observed was around 100 acres
of giant and common salvinia, and less than an acre of water hyacinth and duckweed. The
majority of the giant salvinia was around the Big Creek/ Little Saline/ Saline Lake area. The
lake was about six inches below pool stage due to low rain conditions. The low amount of
vegetation observed was due to several days of freezing temperatures during the 2017 winter
and a prolonged high water during the spring and summer of 2018.
A vegetation survey was conducted on August 5
th
and 6
th
, 2019. Due to the prolonged high
water, there was very little submersed or emergent vegetation. Floating vegetation consisted
of giant and common salvinia. There was approximately 300 acres of common salvinia and
400 acres of giant salvinia. Common salvinia was found from Indigo Bayou east to Larto
Lake, observed mainly in the backs of bayous and in the Shad Lake area. Giant salvinia was
found from Duck Bayou west to Big Creek and Little Saline Bayou. Vegetation coverage is
expected to increase during the summer months, especially giant salvinia. The prolonged
high water in 2019 has moved the salvinia to areas of the lake that the plant had not been
observed in the past. Some of these areas, due to large amounts of buttonbush (Cephalanthus
occidentalis) and American lotus, have the potential to become severely infested in the
summer months. With a mild winter, giant salvinia may cover approximately 1,000 acres or
more in 2020. Other vegetation is expected to return as in normal years.
Limitations:
• The system is prone to extreme water level fluctuations
• Agriculture irrigation may limit timing and use of certain herbicides
• Slow drawdown rate when dewatering approximately one inch per day maximum
Factors that may limit the ability of LDWF to control aquatic plant problems in the water
body:
• 2,4-D waiver area from March 15 to September 15
Past Control Measures:
Biological:
2017: 62,670 giant salvinia weevils (Cyrtobagous salviniae) were stocked in various
locations around Saline Lake, Big Creek, and Little Saline Bayou.
2018: 6,750 weevils were stocked. Low numbers stocked due to high water.
2019: 61,233 weevils were stocked in Muddy Bayou.
Chemical:
Foliar applications of contact herbicides have been used to maintain boating access. Types
of vegetation and acres sprayed are listed below.
Herbicides have been applied at the following rates:
2,4-D: Used at a rate of 0.50 gallons per acre to treat water hyacinth and American
lotus.
Glyphosate: Used at a rate of 0.75 gallons per acre to treat alligator weed, water
hyacinth, American lotus, giant salvinia and common salvinia during the active growing
period.
Diquat: Used at a rate of 0.75 gallons per acre to treat water hyacinth, and salvinia
during the slower growing period or winter months.
Surfactant is added at a rate of 1:4 (surfactant: herbicide) for all herbicides.
Since 2012, herbicide applications for the treatment of giant and common salvinia have
included the following:
April 1-October 31: glyphosate (0.75 gal/acre)/diquat (0.25 gal/acre)/Turbulence (0.25
gal/acre)
November 1 – March 31: diquat (0.75 gal/acre)/non-ionic surfactant (0.25
gal/acre)
Vegetation Spraying History
Spraying is conducted annually in the lake complex, primarily to maintain shorelines near
homes and camps. Boating access in the numerous bayous is also maintained as necessary.
Since 2008, spray efforts to control common salvinia have increased. Spray efforts in 2010
were minimal, and no spraying was conducted in 2011. However, in 2012, over 1,500 acres
were sprayed. The majority of this was to control common salvinia and water hyacinth.
Following the discovery of giant salvinia in October 2012 near the Open Bayou boat ramp,
the area was surveyed and sprayed every couple of weeks until giant salvinia was no longer
observed.
Giant salvinia was discovered again in 2016 around the Open Bayou/ Little Saline Bayou
area. During that year, several high water events occurred. These events spread the giant
salvinia throughout the west side of the complex. After the flooding, giant salvinia could be
found from Big Creek to the east side of Saline Lake. LDWF spray crews and private
applicators conducted multiple foliar applications by boat. In 2017, an aerial treatment was
conducted to treat American lotus and giant salvinia mixed around the west and south end of
Saline Lake and connecting bayous.
High water events occurred in both 2018 and 2019. These high waters have increased the
area that giant salvinia is present throughout the complex and in sloughs and ponds not
normally connected to the lake during normal pool stage. Some of these areas contain a
mixture of common and giant salvinia. Due to the prolonged high water event in 2019, much
of the salvinia was inaccessible to spraying during the year.
Aquatic
Vegetation
Spray Efforts
Year
Acres Vegetation
2005
70
Water hyacinth
88
Giant cutgrass (Zizaniopsis
miliacea)
2006
75
Water hyacinth
2008
94
American lotus
65
Water hyacinth
29
Common salvinia
2009
90
Common salvinia
31
Alligator weed
61
Water hyacinth
2010
63
Alligator weed
9
American lotus
49
Common salvinia
6
Hydrilla
2012
110
Alligator weed
158
American lotus
33
Water pennywort
57
Water primrose
523
Common salvinia
31
Giant salvinia
750
Water hyacinth
2013
51
Alligator weed
47
American lotus
177
Common salvinia
38
Giant salvinia
249
Water hyacinth
2014
268
Water hyacinth
2015
34
Alligator weed
11
American lotus
56
Common salvinia
81
Water hyacinth
2016
57
Alligator weed
277
Common salvinia
370
Giant salvinia
17
Water hyacinth
2017
509.2
American L
lotus
5
Common salvinia
1528.6
Giant salvinia
194.7
Water hyacinth
2018
16.6
Alligator weed
10
Buttonbush
4
Common salvinia
620.8
Giant salvinia
13.1
Water hyacinth
2019
564
Giant salvinia
8
Common salvinia
Recommendations:
A drawdown is recommended in 2020 for the purpose of aquatic vegetation reduction. The
many coves, bayous and areas of dense buttonbush and cypress trees limits access for foliar
spraying. The drawdown should be initiated the week of June 1, 2020.
The target level for the 2020 drawdown will be 3-4 feet below normal pool elevation. The
timing and depth of the drawdown was selected to create the longest drying period, and still
allow access to the lake for foliar spraying.
The drawdown gates will be closed no later than November 1, 2019. The LDWF staff will
work with DOTD personnel to operate the control gate to fluctuate the water level in an
effort to maintain the 3-4’ below pool drawdown goal.
LDWF spray crews will continue foliar spraying of floating and emergent vegetation in
accordance with the approved LDWF Aquatic Herbicide Application Procedure:
Plant Species
Herbicide
Surfactant
Common/Giant Salvinia
(Salvinia spp.)
(April 1 to October 31)
Glyphosate (0.75 gal/acre)
+ Diquat (0.25 gal/acre) or
Clipper SC (2 oz./acre)
Turbulence (or approved
equivalent, 0.25 gal/acre)
Common/Giant Salvinia
(November 1 to March 31)
Diquat (0.75 gal/acre)
Nonionic surfactant (0.25 gal/acre)
Water Hyacinth (Pontederia
crassipes)
2, 4-D (0.5 gal/acre)
Nonionic surfactant (1 pint/acre)
Water Hyacinth in waiver areas
(March 15 to September 15)
Glyphosate (0.75 gal/acre)
Nonionic surfactant (0.25 gal/acre)
Alligator Weed (Alternanthera
philoxeroides)
(undeveloped areas)
Imazapyr (0.5 gal/acre)
Turbulence (or approved
equivalent, 0.25 gal/acre)
Alligator Weed
(developed areas)
Imazamox (0.5 gal/acre)
Turbulence (or approved
equivalent, 0.25 gal/acre)
American Lotus (Nelumbo
lutea)
2, 4-D (0.5 gal/acre)
Nonionic surfactant (1 pint/acre)
American Lotus in waiver areas
(March 15 to September 15)
Glyphosate (0.5 gal/acre)
Nonionic surfactant (0.25 gal/acre)
American Lotus in waiver areas
with potable water intakes
(March 15 to September 15)
Triclopyr (0.5gal/acre)
Turbulence (or approved
equivalent, 0.25 gal/acre)
Duckweed (Lemna spp.)
Diquat (1.0 gal/acre)
Nonionic surfactant (0.25 gal/acre)
Cuban Bulrush (Oxycaryum
cubense, sedge)
2, 4-D (0.5 gal/acre)
Nonionic surfactant (1 pint/acre)
Cuban Bulrush (sedge) in
waiver areas
(March 15 to September 15)
Glyphosate (0.75 gal/acre)
Nonionic surfactant (0.25 gal/acre)
Water Lettuce (Pistia stratiotes)
Diquat (1.0 gal/acre)
Nonionic surfactant (0.25 gal/acre)
Giant salvinia weevils will continue to be stocked into areas of the complex that are
conducive to their establishment as they are available.
Typemap
Larto-Saline vegetation survey conducted on July 24-25, 2013.
Saline/Larto Complex Typemap conducted September 2006 by Dave Hickman
Figure 1. Type map of aquatic vegetation in Larto-Saline Complex (see key below).
A-1: American lotus (moderate to severe to 8 ft. deep), water primrose (moderate to severe)
A-2: American lotus (severe to 8 ft.), hydrilla (moderate to 3 ft.), water hyacinth (light)
A-3: duckweed (moderate), Brazilian elodea (moderate to 6 ft.), fanwort (severe to 6 ft.)
A-4: alligator weed (moderate), arrowhead (moderate), coontail (moderate to severe to 7
ft.), fanwort (moderate to 5 ft.), filamentous algae (light to 5 ft.), fragrant water lily (light),
hydrilla (moderate to severe 7 ft.), southern naiad (light to 5 ft.), water primrose (moderate)
A-5: American lotus (light to severe to 8 ft.), hydrilla (moderate to 3 ft.)
water hyacinth (light)
A-6: American frog’s-bit (light), American lotus (light to severe to 5 ft.), arrowhead (light),
duckweed (light), hydrilla (light to moderate to 4 ft.), water hyacinth (light)
A-7: American frog’s-bit (light), American lotus (light to severe to 5 ft.), arrowhead (light),
common salvinia (moderate), duckweed (light), hydrilla (light to moderate to 4 ft.), water
hyacinth (light)
A-8: American frog’s-bit (light), American lotus (severe to 12 ft.), arrowhead (light),
common salvinia (moderate), duckweed (light), hydrilla (light to moderate to 4 ft.), water
hyacinth (light)
A-9: alligator weed (moderate), American frog’s-bit (light), bulrush (light), common
salvinia (moderate), filamentous algae (light),
A-10: alligator weed (moderate), American frog’s-bit (light), American lotus (moderate to 8
ft.), common salvinia (moderate), filamentous algae (light)
A-11: filamentous algae (moderate to 4 ft.)
A-12a, A-12b: American lotus (light to 4 ft.), arrowhead (light), common salvinia (light),
hydrilla (moderate to 3 ft.), water hyacinth (light)
A-13: common salvinia (light), duckweed (moderate), hydrilla (moderate to 3 ft.), water
hyacinth (severe), water primrose (light)
A-14: American lotus (severe to 3 ft.), hydrilla (severe to 3 ft.), water hyacinth (light)
SALINE-LARTO COMPLEX VEGETATIVE TYPEMAP – 2007 by M. Ewing
The Saline-Larto Complex is a large natural backwater complex located in east central
Louisiana (Catahoula, LaSalle, Avoyelles and Rapides parishes) composed of Larto Lake,
Saline Lake, Shad Lake and numerous interconnecting smaller lakes and bayous. The
complex receives regular backwater flooding from Red River, Black River and Little River.
In any given year, the dominant source of flooding as well as the extent and duration of
flooding can influence fisheries production and aquatic weed growth.
Water Body Information:
Water body type – natural backwater lake
Date Impounded – N/A - natural lake not an impoundment; spillway built in 1958
Surface Area – approximately 8,000 acres at pool stage elevation of 37.0 ft. MSL.
Watershed Ratio – around 100,000 acres; variable depending on flooding
Average Depth – around 7 feet; max depth at pool is around 15 feet.
Drawdown Capacity – 5.5 feet but drawdown rate is extremely slow, less than ½ inch per
day.
Backwater flooding – regularly receives backwater flooding
Nuisance Aquatic Problem:
Submersed – Hydrilla, Egeria, fanwort, coontail
Surface – American lotus, water hyacinth, frog bit, alligator weed, primrose, southern water
grass, common salvinia
In recent years, stabile water level conditions resulting from the lack of normal spring rainfall
and backwater flooding, along with mild winter temperatures have favored the spread of
aquatic weeds. Overall vegetative coverage is about 30% of the 8,000-acre complex’s total
surface area but coverage is much higher in some localities and is restrictive to boating and
fishing access.
Limitations:
Cotton growing area – restrictions on use of 2, 4-D
Proposed Control Measures:
Biological – Not recommended
Chemical –
Water Hyacinth and Other Surface Vegetation – Surface spray with 2, 4-D and glyphosate
for maintenance control of water hyacinth, lotus, primrose, etc. and Reward for common
salvinia.
Hydrilla and Other Submersed Vegetation - Sonar recommended in Shad Lake and major
boat lanes; spot treat with Aquathol in Larto Lake (see map and description of treatment
areas below).
At this time, the main problem areas are in the major boat lanes going into Saline Lake
(includes Big Creek, Open Bayou, Big Saline Bayou and Muddy Bayou) and the shallows of
the Shad Lake area, a popular fishing spot. In addition to these areas, we also receive a lot of
complaints concerning the Larto Lake shoreline. While there is only a narrow shoreline
fringe of vegetation in this area, it happens to be the region of highest residential
development with numerous private residences, camps, piers, etc. The total surface area for
all areas considered for treatment for submerged weed control in the Larto-Saline Complex is
around 1,200 acres with an average depth of around 3 feet (total volume of 3,600 acre/feet).
Below is a map of the area followed by descriptions of treatment zones in order of priority,
with plant species listed in order of dominance:
Saline-Larto Complex
Appendix I – Map of the Larto/Saline Lake Complex
APPENDIX II
Saline/Larto Complex Water Control Structure located on Larto Bayou on the South end of Larto
Lake during a high water event. This picture was taken on May 17, 2011. The water level was at
45.76 MSL at the Larto Lake gauge.
.
