Giant Salvinia

Giant Salvinia – The Most Dangerous Plant In Texas/Louisiana Giant Salvinia

I recently had the pleasure of attending the Bi-State Alliance quarterly meeting and the speaker for the occasion was my friend Howard Elder. Elder is an expert Aquatic Habitat Biologist for the Texas Parks and Wildlife Department in Jasper, Texas and this meeting was a follow-up to a previous meeting between Bi-State Alliance, Senator Robert Nichols, TPWD, SRA (Texas and Louisiana) and Louisiana representatives to discuss Giant Salvinia (GS) issues. There were many items discussed at the recent meeting, but for purposes of this article I would like to zero-in on a few that seemed most critical.

Brief History – GS (Salvinia molesta) has been in Texas waters for a number of years and has been documented in least 11 states since 1995. Its first report in Texas involved a single pond near downtown Houston. In the United States, GS began as a popular plant for water gardens that was sold in aquatic nurseries, and in time was introduced to the wild.

Most anglers in our area relate aquatic vegetation to good fishing but that is not the case with GS. This free-floating fern that originated in Brazil has earned a reputation as one of the world’s worst aquatic weeds—and with good reason. The United States Geological Survey calls this weed one of the world’s most noxious aquatic plants. GS is almost impossible to eradicate on larger impoundments and the use of herbicides to control it can be very expensive.

GS grows fast, doubling itself every eight days, and under ideal conditions in the late summer it may in fact double itself in size every five days. Rapidly expanding populations of GS can easily alter aquatic ecosystems by overgrowing and replacing native plants. The dense “mats” formed on the surface of the water prevent light and oxygen from entering and as the ph level is drastically lowered it affects water quality. At the same time, decomposing material drops to the bottom consuming dissolved oxygen that is needed by fish and other aquatic life.

Bottom line – If left uncontrolled .. this plant can basically kill a lake.

GS is not only a threat to our natural resources but a huge threat to the economics of our area. Let’s use fishing as an example. Millions of dollars are pumped into this area each year with direct expenditures such as gasoline, bait, hotel rooms, tackle, dining, etc. GS can severely affect launching, fishing locations and can make much of the lake inaccessible.

GS is also a major problem to recreation since it ruins conditions for swimming, boating, jet skiing and waterskiing. The weed is also capable of clogging irrigation and electrical generating systems.

Floods during the fall of last year caused huge mats of GS to be washed out of backwater areas and out onto the main waters of Toledo Bend. At first report the mats were 300-plus yards wide and about 2 to 3 miles long. The good news is that by having the GS in one area Elder and his TPWD representatives were able to treat the mats successfully with herbicides.

Herbicides – The state of Texas does not sell herbicides. Many feed stores stock aquatic herbicides however; they sometimes do not carry specific surfactants or name brands but can order aquatic herbicides. With the exception of restricted herbicides like 2,4-D, anyone can apply herbicides with a properly submitted treatment proposal and required notifications.  Application of non-restricted herbicides does not require a TDA Pesticide Applicator’s License unless State money is involved in the purchase.

The Aquatic Habitat Enhancement office of TPWD will provide free training for homeowners who wish to apply herbicides in their immediate area. A seminar is planned June 12th, 2010 that will include identification, herbicide selection, equipment options and steps needed to submit formal treatment proposals and notifications.

Applications in Texas require a formal treatment proposal be submitted to the controlling authority (SRA) and the TPWD District Fisheries Biologist. The SRA has the final decision on the approval. Blank treatment proposal forms can be found at:  http://www.tpwd.state.tx.us/publications/pwdpubs/media/pwd_pl_t3200_1066_2.pdf Proposals are good for 6 months. Additional proposals may be submitted as necessary. An example of a form letter for notifications can be found at: http://www.tpwd.state.tx.us/publications/pwdpubs/media/pwd_pl_t3200_1066_1.pdf Treatments may begin 14 days after submission unless notification is received not to proceed. Weevils

Weevils (Cyrtobagous salviniae) – This dark-colored, one-tenth-inch-long weevil has already been used—with great success—in more than 13 countries over 3 continents. The adult female weevil lays her eggs in a cavity that she creates by chewing into the leaf bud of GS. The larvae that hatch then feed on the base of the leaf bud. They eventually tunnel into the rhizomes or sometimes the petioles—the structures that attach the leaves to the stems. The weevil larvae become adults in 17 to 28 days, depending on the weather. That means this species is capable of producing a new generation of hungry young in about a month during the warmer parts of the summer.  The life span of a salvinia weevil it is about 240-260 days. The adults stop laying eggs in the cooler temperatures—the low 70s—in the spring and fall.

State officials released more than 300K adult weevils on the Texas side of Toledo Bend in 2004. Over-wintering of salvinia weevils has been successful and the weevils have been harvested and moved to different parts of Toledo Bend as well as several shipments to Caddo Lake (approximately 31,314 in 2009). The Bi-State Alliance introductions on Toledo Bend last year, using weevils provided by Louisiana, totaled approximately 58,423 adult weevils. A real positive is that herbicide spraying does not seem to affect the weevils. At this time no weevils have been introduced on Sam Rayburn due to the lack of sufficient giant salvinia to support introductions.

Since weevils must be transported in infested GS, any introductions by non-state agency personnel in the State of Texas must be accompanied by an Invasive Species Permit from TPWD. An Interagency GS Control Team is in place with members consisting of TPWD, USFWS, Caddo Lake Institute, LDWF, LSU Texas A&M, UT, USACE, and USDA.

A Memorandum of Understanding (MOU) between TPWD and LSUAC has also been signed to facilitate the exchange of weevils for propagation and introduction of the weevil to infested sites. The TPWD and LDWF are working together on the propagation and release of salvinia weevils.

Regardless of what you hear, there are no differences between Texas weevils and Louisiana weevils. The weevils all originate from the same source – USDA APHIS facilities in Mission, TX, and USACE in Lewisville, TX (LAERF).

Harvesting – Mechanical harvesting equipment currently exists that can be effective in removing GS, however, the efficiency is low and the cost is prohibitive. TPWD does not currently have the manpower or funding required for harvesting efforts. Best/acceptable methods for destroying harvested plants are composting, deposition in a landfill and drying. The placement of barriers to protect a desired area followed by removal of all plants present can be very effective and may not require a formal permit. Small scale removal would not require state involvement unless transport of the plants harvested over land is required.

Water level manipulation (lowering the lake) has proven the most cost-effective tool to reduce severe GS infestations. Strategically used with other methods, water level manipulation may offer the most reliable and effective means of reducing GS infestations. Periodic draw-downs could potentially save thousands of dollars in treatment costs, reduce the need for fall herbicide applications, and help reduce regeneration of salvinia and water hyacinth the following spring. Keep in mind that this process may be recommended to reduce nuisance aquatic vegetation, but only SRA can control the water levels on Toledo Bend. Public comment would certainly be an important part of any decision by SRA regarding any proposed water level manipulation.

So Where Do We Go From Here? Statistics have shown that when GS is found in a lake it is almost always near a boat ramp. This is something that all of us should be aware of as we launch our boats and take them out of the water. A tiny piece of Salvinia hanging on a boat trailer rail or stuck on the outboard motor lower unit is all it takes to get the growing cycle started at a new location. Many of our anglers go from lake to lake and it is very easy to spread
this destructive plant. The state of Texas passed a law in 2005 that requires boaters to remove all harmful plants from their boat trailers and boats or face a criminal citation carrying a fine of as much as $500 … per plant.

I would encourage the idea of having deposit bins located at all of our high profile boat ramps where anglers could place any GS taken from boats and trailers.

Public awareness is certainly one of the most effective and least expensive ways to control GS. We all need to learn to identify these invasive species, remove them if possible and report the sightings to state agencies. If we all play a part in being the eyes and ears of the TWPD and LDWF it can make a big difference in controlling these plants.

The magnitude of the invasive aquatic vegetation problem is huge and if not controlled it is certain to have a dramatic economic and recreational impact on Texas and Louisiana. It’s a fight that will obviously need the coordinated support of our state legislators in providing the proper funding for adequate manpower and treatment methods. We are very fortunate to have Elder and his crew helping us work this issue.

My thanks also to Jerry Clark and the Texas SRA, Jim Pratt and the Louisiana SRA, TPWD, LDWF and any of the other groups that have joined the effort to control this deadly invasive species. A collaborative effort by everyone is required to prevent an ecological and economic disaster that could easily surpass what we experienced during the past horrific low water lake conditions.

FYI – TPWD can accept monetary donations for vegetation control. To assure the donations are used for the purposes intended, a letter can accompany the donation – specify its purpose, a deadline for its use, and return of the donation if the funds are not used.

Any questions regarding GS related issues should be routed to ….
Howard Elder
TPWD Aquatic Habitat Biologist
Rt.2 Box 535
Jasper, TX 75951
Office: 409-384-9965
Fax: 409-384-4984

***Update —

The Texas Parks and Wildlife Department, The Sabine River Authority of Louisiana, The Sabine River Authority of  Texas and the Toledo Bend Bi-State Alliance sponsored a “Giant Salvinia Seminar” Saturday, June 12th (9am-2pm) at Hemphill VFW Post 10351.  Approximately 80 concerned community people showed up for the seminar which also included a free BBQ lunch that was just great!

Howard Elder, Aquatic Habitat Biologist for the Texas Parks and Wildlife Department conducted the seminar with assistance from his staff.  Presentations were made regarding herbicides, the process for using the herbicides, proper paperwork involved, Salvinia weevils and many other topics related to GS. 

As usual Mr. Elder and his staff did a great job and my compliments to the Toledo Bend Bi-State Alliance for putting the seminar together.  Many questions were asked by the attendees and I think everyone left with a better appreciation of the issue and what we need to do to successfully fight this dangerous aquatic plant. 


Also brought up at the meeting was the concern that many areas of the lake have a combination of plants (not
GS) that seem to be increasing in size and are making swimming and fishing in those areas difficult.  The plants are a combination of Alligator Weed (on the surface) and Eurasian Milfoil and Filamentous Algae under the surface.  The Eurasian Milfoil has been on Toledo Bend for years and may well be the dominant submerged vegetation present on Toledo Bend.  These plants are vulnerable to herbicides but in most cases the homeowners are just raking out the plants so they can swim, etc. around dock areas. 

. Howard Elder discusses GS issue SRA Texas members in attendance Howard Elder and local angler Bill Huegel Crowd watches slide presentation Alligator Weed Alligator Weed and Eurasian Milfoil

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