Passing the Torch

The Center for Invasive Species Eradication program that funded the construction of the weevil rearing facility at the Caddo Lake National Wildlife Refuge and much of the salvinia weevil research over the last four years has come to an end. Funding for the program expired in July 2014.

Prior to its closing, plans were made to transfer the greenhouses at the refuge over to the Texas Parks and Wildlife Department to operate. They will continue to raise as many weevils as possible at this facility for use at Caddo and other lakes in the area.

Assistance was also provided to the Greater Caddo Lake Association of Texas and the Caddo BioControl Alliance, a newly forming non-profit organization that will manage the "Morley Hudson Weevil Greenhouse at Caddo Lake." This is a true grass roots effort to deal with the giant salvinia on Caddo Lake with local resources. Lofty goals have been set for this facility, but with continued support and perseverance, significant progress can be made. To learn more about this facility and contribute to the cause, visit the Greater Caddo Lake Association of Texas website. In the video below, GCLA President Daren Horton gives an overview of the newly established facility.

Salvinia Weevil Research at Caddo Lake...The Next Viral Videos: Part One

A few weeks ago, Jack Canson, a local advocate for Caddo Lake shot some video at the Giant Salvinia Weevil Rearing Facility at the Caddo Lake National Wildlife Refuge that explains the program and the progress made over the last 4 years...all in less than 10 minutes of video!  They are single take videos, so they are definitely no polished Presidential speech or anything like that. Regardless, they get to the point and describe the great local support for the effort as well as the lessons learned over the years.



Thanks Jack for shooting, editing and posting these videos.

Giant Salvinia Weevil research at Caddo Lake...The Next Viral Videos: Part Two

Installment two.

Giant salvinia weevil research at Caddo...The Next Viral Videos: Part 3

And here is the third and final installment.

Grass Roots Rising Up Against Giant Salvinia

A new project is underway on the banks of Caddo Lake in an effort to take back the lake. Giant salvinia has had its grips on the lake for nearly a decade now and shows no sign of slowing down. Harsh winters will set it back, but only for a while. Chemicals will knock it out, but it comes back. The past 6 months have seen salvinia coverage on the lake reach its highest level yet only to be pummeled by several rounds of extended cold. Through it all, the threat of salvinia remains great.

This lingering threat and the desire to "keep Caddo Lake Natural" is really the driving force behind a grass roots effort to do something about giant salvinia. The Greater Caddo Lake Association of Texas (GCLA) began fund rasing last year and has now begun construction on a lake side salvinia weevil rearing facility. This facility will be similar to the Center for Invasive Species Eradication (CISE) facility at the Caddo Lake National Wildlife Refuge and a sister facility operated by the Texas Parks and Wildlife Department.

A key difference in the GCLA facility and the CISE facility is their primary mission: production vs. research. Being located on the Lake, the GCLA facility will have access to a ready supply of water that is quite suitable for salvinia growth. Easy lake access is another benefit as is the publicity that the facility will receive on the lake's shore.

Much work is left to be done, but GCLA hopes to have the facility up and running early in the 2014 growing season. They of course can use your support and appreciate help in spreading the word. Visit their website at www.gclaoftx.com.

They also have some YouTube video to help explain what they are doing. Check it out below. http://youtu.be/pKe3xvEEjpY

AgriLife Today highlights salvinia weevil work on Caddo Lake

AgriLife Today, Texas A&M AgriLife's news media outlet, published a story this afternoon highlighting the impacts of the giant salvinia weevil at Caddo Lake this year. In the article titled "AgriLife project weevils damaging invasive giant salvinia at Caddo Lake," they highlight the progress made in the effort to establish weevil populations on the lake and document the impacts they are having on the current giant salvinia population. To read the full story, visit http://today.agrilife.org/2013/11/22/agrilife-project-weevils-damaging-invasive-giant-salvinia-at-caddo-lake/.

Weevil impacts at one of the release sites in November 2013. Open water and salvinia darkening in the background is caused by weevil damage to the plants.

Last Year's Weevil Impacts Bigger than Expected!

Last Friday, Dr. Allen Knutson and Lee Eisenberg made it out to the Back Lake/Bird Roost area of Caddo Lake where weevil releases made in 2012 to confirm the presence of suspected salvinia weevil damage. What they found was extremely encouraging. The salvinia mat at this site was almost completely destroyed with only a few primary and secondary stage plants present over approximately 10 acres or more. 

The density of weevils present at this site confirms that weevils are responsible for this damage. Samples processed from this site averaged 77 adult weevils per kilogram of sample. With about 40 weevils per kilogram of salvinia being the target density to achieve salvinia control, this threshold has been far exceeded.

Since no weevils were released at this site in 2013, these finding prove that the weevils successfully over-wintered at this site on Caddo Lake this past year.In fact, more weevils made it through the winter here than anticipated! Now we can only hope that weevils continue to survive the winters. If so, the weevils' impact can be expected to grow in the coming years!

Go forth and prosper weevils!

2012 weevil release site showing extensive weevil damage and only scattered primary and limited secondary giant salvinia present. Weevils overwintered at this site and have impacted 10 acres or more! (photo by Dr. Allen Knutson, November 1, 2013)

Last Year's Weevil Making Their Presence Known

In the summer of 2012, the primary weevil release site was in the Back Lake area of Caddo Lake. This site was chosen as it is a relatively isolated area of the lake with little boat traffic, it maintained water throughout the 2011 drought and has a dense Cypress break that provided a relatively stable habitat for the weevils. Flow in this area is also relatively calm and typically results in floating vegetation staying in place. One downfall of this release site is the difficulty in getting to this area when lake level drop. Toward the end of 2012 when the water level dropped, it became impossible to enter this site by boat and the team had to wade in to sample weevil populations.

Fast forward one year to 2013. The Back Lake area was abandoned as a release site due to it inaccessibility during low lake levels. That said, this area has been checked out this year to see if the weevils released last year remained in the area and if they were having any impact on giant salvinia.

The short answers to those questions are Yes and Yes! Photos taken at this site show considerable damage to the giant salvinia at this site and a decent amount of open water present as well. We will be going out to this site in the next few weeks to collect samples so the weevil density can be counted and will also survey the surrounding area to see if any other weevil damage can be found.

Weevil damage at the 2012 weevil release site in Back Lake. No weevils were released at this location in 2013.

This find is really encouraging as it shows that the weevils released in earlier years survived the winter in large enough numbers to have a noticeable impact on giant salvinia. While this is only a small success, it is still a success!

Weevils Making an Impact on Caddo

Now that summer is officially over and we move toward the winter months salvinia weevil numbers in the release site have increased to the point where obvious plant damage from the weevils can be seen. Over the course of the spring and summer months, more than 50,000 weevils have been released into an isolated area of Caddo Lake. This may seem like a lot, but when you have about 7,000 or 8,000 acres of salvinia, 50,000 weevils don't cover much ground.

Controlling, or impacting salvinia with weevils is essentially a numbers game. You must have a high enough weevil density, a a sufficient number of weevils per kilogram of salvinia before visible damage is obvious. A weevil density of about 40 adult weevils per kilogram of salvinia is typically that magic level. And the good news is that the weevils we released this year have finally gotten to that point.

According to Lee Eisenberg, the weevil density in July was about 6 weevils per kilogram. By August the density was up to 15 per kilogram and increased to 34 in September. The October sampling hasn't been completed yet, but photo evidence suggests that weevil numbers have now surpassed 40 per kilogram.

The photo below was taken the first week of October and clearly shows a "sick looking" area of salvinia in the release site. Additionally, weevil damage is obvious moving away from the release site as well.

Weevil damage to giant salvinia at the release site in early October 2013

While this is only a small success, it is still a success that shows the utility of salvinia weevils. It also reiterates the need to have more weevils on Caddo Lake. Additionally, the facts that weevil reproduction is driven by temperature and that the point in the year that population numbers reach the 40 per kilogram threshold is driven by when reproduction begins highlight the need to find weevils that are adapted to colder climates and reproduce at colder temperatures.

Additional Support for Caddo coming from Harrison County Commissioners

In yesterday's Harrison County Commissioner's Court meeting, the court approved an additional $2,000 to "support the Cypress Valley Navigation District's eradication and research efforts regarding the critical invasion of giant salvinia on Caddo Lake" according to an article by Robin Richardson in today's Marshall News Messenger.

Additionally, the Labor Day weekend fundraiser hosted by the Greater Caddo Lake Association netted more than $10,000 that will go toward helping control giant salvinia on the lake.

Harrison County Judge Hugh Taylor said he hopes that these local contributions of additional funding will encourage other entities to help with the control efforts as well.

One thing is for certain; every little bit of additional funding that goes to Caddo Lake will certainly help.

Support for the Fight Against Giant Salvinia Spreading

Just like Giant Salvinia, support for any and all efforts to fight this floating aquatic invasive plant is spreading. In a Saturday article from the Marshall News Messenger, additional funding from the Harrison County Commissioners Court was on the agenda for their Monday, September 8th meeting.

US Congressman Louie Gohmert who represents the area also provided his support for the efforts and need to continue them out at Caddo Lake. Not only did he encourage everyone to visit Caddo Lake and enjoy the lake's unique natural beauty, he also commended the efforts of the Center for Invasive Species Eradication's weevil rearing operation at the Caddo Lake National Wildlife Refuge and the work being done with the salvinia weevil. As the Congressman mentioned, the salvinia weevil does show promise for being able to manage giant salvinia levels in lake at some point in the future, but it will take time and a large number of weevils....both of which are in short supply. 

For now, research at the weevil rearing facility is focused on producing weevils and trying to identify a more cold tolerant strain of weevil that may be more able to withstand the sometime harsh winters that Caddo Lake can experience.

Congressman Gohmert takes a closer look at the salvinia weevil during an August 2012 visit to the weevil rearing facility at the Caddo Lake National Wildlife Refuge

In addition to support from elected officials, local support has greatly increased as well. People are volunteering time and resources to try and get a handle on the giant salvinia issue. Hopefully, weevil production capacity will increase through this increased interest and a step closer to managing giant salvinia can be taken.

Until then, keep up the good fight. And to borrow the "Take Care of Texas, It's the Only One We've Got" tag line from TCEQ and Kevin Fowler; Take Care of Caddo, It's the Only One We've Got"

Support for Weevils Grows...So does Giant Salvinia

This year has turned out to be a bad one for Caddo Lake in terms of giant salvinia coverage. Recent estimates have put the total number of acres covered in the Texas portion of the lake alone somewhere north of 6,000 acres. This level of infestation has drastically reduced use of the lake as boats easily get stuck in the floating mats of giant salvinia that cover the upper ends of the lake.

On a positive note, local support has grown significantly and the use of salvinia weevils is now viewed as the best, long term solution to the problem. In fact, the Greater Caddo Lake Association is hosting a benefit barbeque this Labor Day weekend that will expand the production capacity of weevils around Caddo Lake. An article in Sunday's Marshall News Messenger provides details of the event and further describes the dire situation at Caddo Lake this summer. If you can, please make plans to attend this great event and help support efforts to protect this beautiful lake.

Giant salvinia completely covers Boat Road C on Caddo Lake. Similar coverage of salvinia is present across more than 6,000 acres of Caddo Lake in Texas this summer.

Caddo Lake Giant Salvinia Control Program Updates

It has been a while since the last blog post, but rest assured that the fight against giant salvinia at Caddo Lake has been in high gear. With a relatively mild winter experienced this last year, giant salvinia levels on the lake coming into the spring were already nearing their highest levels in years. One positive of the mild winter was that weevil populations did survive the winter; however, higher water around the first of the year dispersed the remaining weevils widely across the lake.

Extensive giant salvinia coverage during May 2013 along boat road C near Joe Moore Hole

On the biological control front, one weevil release has been made from the Caddo Lake Salvinia Weevil Rearing Facility so far this year and a second release is being planned for the near future. An estimated 34,400 adult weevils were released along with an untold number of larvae and eggs. These weevils were released into backwater areas of the lake where they are least likely to be disturbed.

Weevil research has continued as well and is showing promising results:

- Small frame studies showed that salvinia weevils were able to reduce giant salvinia biomass by 50%

- A "Chill Coma Recovery Test" was conducted to evaluate salvinia weevils resuscitation time following an extended period freezing. Weevils from Australia resuscitated first followed by those from North Texas (Lewisville), South Louisiana (Houma) and from Florida. This suggests that weevils can adapt to localized weather conditions to some extent.

- "Solid Freeze Time Trials" were also conducted to evaluate the weevil's ability to tolerate weather extremes. Weevils were frozen solid for 24, 30 and 36 hours respectively and survival was documented. At 24 hours, survival was good for all weevils; however at 30 hours, Australian weevils survived far better than any weevils from the U.S. At 36 hours of freezing, weevil survival in all samples was greatly reduced.

- Efforts are also underway to collect weevils from higher elevations (cooler areas) in their native ranges in Argentina. Once received, their genetic make up will be evaluated and they will be subjected to "Chill Coma" and "Solid Freeze" tests to determine their ability to tolerate cold weather extremes.

The Problem Spreads

Earlier this week, an article in the Austin American Statesman revealed a growing problem in northeast Texas lakes....giant salvinia. According to Texas Parks and Wildlife Biologist Lynn Wright, lakes with recently reported giant salvinia infestations include Lake O’ The Pines, Gilmer, Murvaul, Wright Patman and Lake Welch.

This recent rash of infestations highlights the need to raise awareness about the dangers of this plant. It's rapid growth rate and lack of natural enemies in Texas give it a competitive advantage in almost any water body. Preventing new infestations is much easier than managing infestations once they arrive and as such TPWD is asking boaters to be extra vigilant about checking and cleaning their boats and trailers both before they launch and after they load.

 

To read the full article in the Statesman, click the link below.

http://www.statesman.com/news/sports/troublesome-plant-continues-to-spread-in-texas-lak/nWHkH/  

How Should Homeowners Deal with Salvinia?

In a recent article in the Marshall News Messenger titled "Before treating salvinia, residents must file paperwork", Tim Bister, Texas Parks and Wildlife Department's district supervisor and fisheries biologist in the Caddo Lake area discussed appropriate steps for homeowners and landowners around Caddo Lake to take if they want to fight giant salvinia on their own.

Caddo Lake is a public water body and as such, is managed by the state.  To deal with nuisance or invasive aquatic vegetation like that commonly present at Caddo Lake, the state requires that a document known as an Aquatic Vegetation Treatment proposal be filled out. What these documents do is outline the type of aquatic vegetation (floating, emergent or submerged), the target aquatic vegetation species name, the estimated amount of aquatic vegetation acreage to be treated, and the proposed treatment type (mechanical, biological or chemical). A map also accompanies these treatment proposals as well and helps TPWD ensure that there aren't any conflicting treatments planned.

While the article provides more specific information about Aquatic Vegetation Treatment proposals, it is always a good idea to contact the TPWD District office to discuss plans. In the Caddo Lake area, TPWD's District Office is located at 3802 East End Blvd. So., Marshall, Texas 75672. You can also contact them by phone at (903) 938-1007.

http://www.marshallnewsmessenger.com/news/before-treating-salvinia-residents-must-file-paperwork/article_50f99050-e992-55b3-bf62-409eab8f50de.html

Cautiously Optimistic About Progress

Through the summer and into the fall salvinia weevils were released by the Center for Invasive Species Eradication team and local volunteers in the upper portions of Caddo Lake where giant salvinia had firmly established itself.  While results were not dramatic, optimism is building that weevils are having an impact on giant salvinia. Lee Eisenberg described this small success in a recent article in the Marshall News Messenger.

http://www.marshallnewsmessenger.com/news/researcher-cautiously-optimistic-weevil-is-eating-salvinia/article_c8d23f7a-87c7-5751-9ae0-b33abd6c4cc3.html

Efforts will continue in the spring with the release of additional weevils into the back water areas of the lake in hopes of weevil populations expanding enough to yield visible results.

Lee Eisenberg wades through damaged salvinia in September 2012. The browning of the salvinia indicates that it is not a healthy plant and is in the process of dying.

Interagency Giant Salvinia Control Team Meeting Highlights

On October 16th, 2012 the Interagency Giant Salvinia Control Team convened in Karnack at the community center to discuss recent research findings, speak of control successes and plan for the future. Representative from the Caddo Lake Institute, Cypress Valley Navigation District, Louisiana Department of Wildlife and Fisheries, Louisiana State University Ag Center, Northwestern State University, Texas A&M AgriLife Research and Extension, Texas Parks and Wildlife Department, Texas Water Resources Institute's Center for Invasive Species Eradication, U.S. Army Corps of Engineers, and U.S. Fish and Wildlife Service personnel all spoke of efforts underway to combat giant salvinia biologically and chemically.

Biological control using the salvinia weevil  (Crytobagous salviniae) garnered the bulk of discussion. LSU Ag Center, Texas A&M AgriLife, Texas Parks and Wildlife and the U.S. Army Corps of Engineers are all working to mass produce and research the salvinia weevil and each had progress/success to report as well as planned research to discuss.


Some brief highlights from these groups include:

- effective giant salvinia control is being seen in several location including southern Louisiana and B.A. Steinhagen Lake near Jasper, TX.

- cold tolerance studies revealed significant differences in weevils from Texas, Louisiana, Florida and Australia to tolerate extended freezing

- chemical toxicity trial show that neither chemical nor surfactants commonly used to treat giant salvinia are toxic to the salvinia weevil

- chemical trials reveal effectiveness of chemical/surfactant combinations, but none tested are 100% mortal to giant salvinia


 Ongoing and planned work includes:

- evaluate what factors cause weevils to take flight; assess how well they can fly and what distance they can cover

- work to import weevils from colder climates such as the Argentinian highlands or southern Brazil 

- evaluate combined biological and chemical treatments and evaluate control success

- test impacts of aerial chemical applications in winter through dormant tree canopy


Collectively, the meeting was filled with positives and all parties involved were optimistic about the progress being made. With fair weather and time, the salvinia weevils seem to be well on their way to making a significant dent in giant salvinia infestations. The threat of cold temperatures loom though, and more work to identify strains of the weevil that can tolerate these colder temperatures and begin reproducing earlier in the spring are critical to the successful use of weevils in areas like Caddo Lake that experience periodically cold winters. 

Weevils Numbers Increasing on Caddo

As a part of the efforts to use biological control to suppress giant salvinia at Caddo Lake, monthly surveys are conducted to evaluate weevil populations at the salvinia weevil release site. During the last sampling event conducted on September 20, 2012 by Texas A&M AgriLife Extension Service scientists Dr. Allen Knutson, Dr. Abhishek Mukherjee and Mr. Lee Eisenberg discovered considerable giant salvinia browning. While this is not the drastic reduction in salvinia like what was seen at Lake Steinhagen, this is still proof that the weevils are working.

Lee Eisenberg collects salvinia samples on 9/20/2012 to evaluate salvinia weevil density. The browning of the salvinia here is caused by salvinia weevil damage.

Samples are collected by gathering salvinia in large Ziploc bags. These samples are returned to the lab at the Caddo Lake National Wildlife Refuge where they are weighed and subsequently dried in Berlese funnels. The salvinia is held in a metal funnel and a light/heat source is applied above the salvinia which dries the salvinia and causes the weevils to migrate away from the heat. In this case, the weevils move down and into a Mason jar where they are easily counted.

Berlese funnel used to count salvinia weevils. 

In this and all sampling events, 16 samples are processed each weighing in at 500 grams, or 0.5 kilograms. In total, 178 adult weevils were collected during this event yielding a density of 22 weevils per kilogram of salvinia. This is really good news and shows that weevil numbers are rapidly increasing on the lake. In fact, the weevil population has increased over 500% during the month since the August sampling when only 33 weevils were collected. Another positive finding is that almost 19% of the weevils collected were brown in color indicating that they are very young. These young weevils and other weevils hatched between now and the end of the growing season are those most likely to survive all the way through the winter due to their early stage in life.

So, we are hopeful that the winter will provide hospitable conditions to the weevils and that numbers on the lake will reach levels where effective control is seen. For now, we are pleased with the success that we are seeing and hope it continues.

Steinhagen Success

In a recent news release, the successful application of the salvinia weevil to control giant salvinia on Lake Steinhagen was showcased (http://today.agrilife.org/2012/09/20/weevils-successfully-destroy-acres-of-lake-invading-plants/). In a coordinated effort, the US Army Corps of Engineers (USACE) has been working with the Texas Parks and Wildlife Department (TPWD) Aquatic Habitat Enhancement Program staff from Jasper to use the salvinia weevil to combat giant salvinia on the lake. In late 2010, TPWD began releasing weevils on one area of the lake and through March of 2012 had released about 112,000 weevils. During this time, USACE did not apply chemicals to this area in an effort to see what the weevils were capable of. The pictures clearly describe their capabilities under good conditions.

Giant salvinia coverage on upper end of Lake Steinhagen, April 2012

In April 2012, giant salvinia was estimated to cover about 300 in this area of Lake Steinhagen. By August, the coverage area was conservatively estimated at only 150 acres and had led to open water in the middle of that area. What giant salvinia remains is isolated to the edge of the lake and mats of other vegetation. While the weevils haven't removed all the giant salvinia, they do show the ability to manage giant salvinia when it is present. 

Same area of Lake Steinhagen, August 2012

In an effort to get some more research bang for the buck, Dr. Abhishek Mukherjee of the Center for Invasive Species Eradication team worked with TPWD and USACE personnel to study the weevil population dynamics and document their impacts. Some of their findings describe why and how this successful reduction in giant salvinia came about this year.

In February and March 2012, documented weevil densities were in the 20 to 30 weevils per kilogram of giant salvinia range indicating that a sizable population of weevils had survived the winter on Lake Steinhagen. These relatively high numbers of weevils coming out of the winter enabled the population to expand rapidly. By late July, weevil numbers had more than doubled to just over 60 weevils per kilogram of giant salvinia. This number of weevils is widely considered the weevil density needed to suppress giant salvinia growth.

Ultimately, we hope to see similar success with biocontrol at Caddo Lake. The challenge is maintaining adequate weevil populations on the Lake through the winter. With Caddo Lake being more that 100 miles farther north than Lake Steinhagen, this may be difficult. Efforts at Caddo continue to explore ways to enhance the cold tolerance of the salvinia weevils and some live weevils were found late this past winter on Caddo, but their numbers were much lower than those on Lake Steinhagen.

So for now, we will continue releasing weevils on Caddo and hope for another mild winter that will allow their populations to persist and flourish early next spring. 

Congressman Gohmert and Staff Visits Weevil Rearing Facility

On Wednesday, August 15th, Congressman Louie Gohmert from Texas' 1st Congressional District visited the Center for Invasive Species Eradication's Giant Salvinia Weevil Rearing Facility as a part of his visit to the district during Congress' summer recess. The Congressman has been actively engaged and supports efforts to quell the giant salvinia infestation at Caddo and other lakes throughout his district. As a member of the House Committee on Natural Resources, Congressman Gohmert routinely deals with issues that impact our nation's natural resources.

While the Congressman has been on Caddo Lake many times and seen the perils of giant salvinia first hand, many of his Staff have not. This stop on the Congressman's trip gave some of his staff the opportunity to see giant salvinia up close and personal while also getting out on Caddo Lake to enjoy its unique beauty.

The first stop on the tour was the giant salvinia weevil rearing facilities green houses. The Congressman and his staff were briefed on the operations of the green houses and weevil production by Mr. Lee Eisenberg. Also mentioned was the great collaboration that has gone into the establishment and operation of the facility. The Texas Parks and Wildlife Department, the Caddo Lake Institute, U.S. Fish and Wildlife's Caddo Lake National Wildlife Refuge staff and many local volunteers were of great assistance to Texas A&M University personnel in getting the facility constructed and underway. 

Moving indoors to the Caddo Lake National Wildlife Refuge headquarters and the lab we have set up there, Lee continued discussions on how weevils are sampled. An adult weevil and weevil larvae were also available to view under a microscope. Adult weevils are about 2 mm in length, so getting a really good look at them requires magnification.

Following the brief stint in the lab, the visit to the weevil rearing facility wrapped up with a short presentation and video. Dr. Allen Knutson discussed work that he and Dr. Abhishek Mukherjee are conducting to evaluate the cold tolerance of the salvinia weevil. Initial findings indicate that weevils from different geographic locations are adapted to their specific climates making some more cold tolerant than others. The video shown (same video as the previous post) highlighted the current giant salvinia situation on Caddo Lake.

Before the Congressman and his staff departed, we took a short boat tour of Caddo Lake. Joining in on the tour was newly elected Texas House of Representatives Member Elect Chris Paddie. He will be representing House District 9 in the coming session. Given the time available, we weren't able to get the group out to the areas of the lake where giant salvinia is really bad. Regardless, everyone was able to truly enjoy Caddo Lake.