Thursday, August 18, 2011

Sen. Hutchison Praises Caddo Lake Giant Salvinia Work

Last week we had the privilege of U.S. Sen. Kay Bailey Hutchison visiting Caddo Lake and touring the Center for Invasive Species Eradication’s salvinia weevil-rearing facility located at the wildlife refuge.

Following the tour, Hutchison spoke to a group gathered at the Caddo Lake National Wildlife Refuge about the threat that invasive species such as the giant salvinia pose to the refuge and to Texas lakes.

“While Caddo Lake is home to hundreds of animal, fish and plant species, invasive species threaten this magnificent resource,” said Hutchison. “We are proud to work with the Caddo Lake Institute and Texas A&M University on creating a center of excellence focused on eradicating invasive species.”

You can read the full AgriLife TODAY story for more information. Visit our Facebook page for more photos of the day's events.

Sen. Hutchison also applauded the Caddo Lake Giant Salvinia Eradication Project in her weekly column in the Mineola Monitor, noting that "this promising research will help restore Caddo's habitats and protect this unique natural treasure." Read the full Mineola Monitor article for more information.

Recap of Congressional Hearing on Giant Salvinia

Back in June, we attended a Congressional hearing in Shreveport on giant salvinia.

Experts at the hearing testified that there is no silver bullet for giant salvinia. They also stressed that research collaboration in combination with various management methods and education is essential to fighting the plant.

Testimony by federal agencies, Texas and Louisiana state agencies, universities and non-governmental organizations on efforts to control and eradicate giant salvinia were heard during the field hearing of the U.S. House of Representatives Subcommittee on Fisheries, Wildlife, Oceans, and Insular Affairs on June 27 at Louisiana State University–Shreveport.

Subcommittee Chairman Rep. John Fleming from Louisiana and Rep. Louie Gohmert from Texas attended the hearing. Staff from the Texas AgriLife Extension Service and the Texas Water Resources Institute (TWRI) attended the hearing.

“We are losing ground on something we don’t have an answer for,” said Robert Barham, secretary of the Louisiana Department of Wildlife and Fisheries. Louisiana has seen its state-wide infestation of giant salvinia grow from approximately 13,000 acres to more than 25,000 acres in two years.

Richard Lowerre, Caddo Lake Institute president, highlighted our work on rearing the salvinia weevils for release into the lake and educating the public, with collaborators Texas AgriLife Research, Texas AgriLife Extension, and the Texas Parks and Wildlife Department.

Dr. Michael J. Grodowitz, U.S. Army Corps of Engineers research entomologist, said the biological control of giant salvinia with salvinia weevils is “highly promising” but said managing the plant through biological control is a long-term process. Grodowitz said besides looking at ways to control the plant, research needs to be done on what underlying factors in a particular waterbody allow the plants to grow and out-compete native plant species.

Other witnesses were Louisiana State Rep. Henry Burns; Ross Melinchuck, Texas Parks and Wildlife Department deputy director; Michael Massimi, Barataria-Terrebonne National Estuary Program invasive species coordinator; Ken Ward, Caddo Parish Department of Public Works project manager; Dr. Randy Westbrooks, U.S. Geological Survey National Wetlands Research Center invasive species prevention specialist; Dr. Dearl Sanders, Louisiana State University Idlewild Research Station resident coordinator; Jeffrey Trandahl, National Fish and Wildlife Foundation executive director; and Dr. Damon Waitt, University of Texas Lady Bird Johnson Wildflower Center senior director.

Read the Natural Resources Committee news release. Listen to the hearing.

Monday, June 6, 2011

Large-Scale Weevil Releases Begin

Over the past month, we've begun releasing the weevil infested material from our tanks onto the largest giant salvinia patches we can find on the lake. We have released large numbers of weevils at three locations and will be monitoring it consistently as summer progresses. We will be releasing at a fourth site in the near future which will complete the number of initial release sites required for the research protocol. Additional large-scale releases will be made as the weevils re-expand their numbers in the tanks and the giant salvinia begins to rapidly expand with the progressing summer heat.

To date, we've released a little over 70,000 weevils in the three locations (and an additional estimated 217,000 weevil larvae that would be within the released plant material). These weevils came from only two tanks in which we removed approximately 80% of the material of each tank. The two tanks had a spring weevil population "explosion" in which the adult weevil population density increased from 8 adults per pound to an estimated 85 weevils per pound! Consequently (and not surprisingly), the salvinia in the weevil tanks quickly began to crash due to this high number of weevils. As a result, every time we're on the water, we bring in fresh giant salvinia off the lake to keep our remaining weevils happy, well-fed, and reproducing. Hopefully, we'll be seeing some progress from the released weevils and will be able to report all findings.

Thanks to Bryan Higdon and Adam Fisher who volunteered their time to help with the weevil releases. Our next large-scale release will likely require more volunteers so we'll be putting the call out at some point later this summer.

Tuesday, May 3, 2011

Hurry Up...and Wait. Salvinia Still Recovering

In late March of 2011, we released approximately 1,500-2,000 weevils into a small area (less than an acre) of semi-green giant salvinia that persisted through the cold winter. We are closely monitoring this release site in hopes of collecting valuable data regarding early season weevil reproduction, weevil feeding activity, as well as environmental variables that may affect overall weevil success.

As of early May, there appears to be few, if any mats of giant salvinia that appear large and green enough for a large scale weevil release (however, the water hyacinth seems to be recovering rapidly). We know this situation will change quickly as we progress into May and early-June; as summer approaches, it's quite possible we'll have many covered areas that will be ideal for weevil releases.

Based upon the preliminary results of our ongoing "weevil egg-laying and larvae cage study", it's clear that lake temperatures are within range for weevil reproduction. This is critical because the larvae (pictured on the right), not the adults, are the most effective in controlling giant salvinia. These 1-2 mm larvae tunnel through the plant rhizome (rhizome is basically the stem connecting the leaves of the plant) causing massive damage to the plant. By dissecting the plants in our cage study, we are finding lots of these larvae doing their work. In fact, the giant salvinia in our weevil tanks are starting to show this larvae-induced damage (shown in the yellow/brown coloration in the bottom picture). Thus, the sooner we can get these bugs out and reproducing, the better.

We are hoping to do our first large scale release in the next 2-3 weeks. Of course, this is anticipating that we have some spots with adequate giant salvinia on the lake. If you are interested in assisting with this and other weevil releases, please email to receive more information. As giant salvinia growth increases and CISE efforts ramp up, look for more updates on the blog and facebook page.

Monday, March 21, 2011

Caddo Lake Community Meeting - April 7th, 2011

The Caddo Lake Community Meeting, hosted by the Caddo Lake Clearinghouse will be on:

DATE: April 7th, 2011
TIME: 5:30 - 7:15 PM

Karnack Community Center
15593 FM 134 (at the intersection of FM 134 and T.J. Taylor Avenue)

  • Aquatic Vegetation Control on Caddo Lake (including talks regarding the Giant Salvinia Eradication Project)
  • Texas Master Naturalists Presentation
  • Texas Mussel Watch Program Presentation
  • Updates on Enviornmental Flows, Paddling Trails, LHAAP Cleanup, and paddlefish establishment
refreshments provided by Caddo Lake Institute

Spring Weevil Study Commences

It's documented that correct water temperature is critical for the development of salvinia weevils. As the water temperature increases from 62.6 F to 69.9 F many activities such as feeding, oviposition (egg-laying), and egg-hatch begin. However, spring temperatures (in a water body such as Caddo) at which these activities begin have apparently not been reported. Therefore, a study has begun to determine the temperature and date in which egg-laying occurs on Caddo Lake. It's hoped that the results will help further guide our efforts to control giant salvinia using weevils.

To do this, 30 cages (the same cages from the overwintering study) containing 12 adult weevils with fresh salvinia along with temperature loggers were placed on the lake last week. Each week for the next 10 weeks, three cages will be removed at random and the salvinia within will be extensively searched for adults, newly emerged adults (which will have a red color), and any larvae present (larvae will be found tunneling through the rhizome of the plant). We will be looking for the time and temperature at which "significant numbers' of larvae are present in all the cages.

Also, some recent local publicity regarding Caddo Lake and this project appeared in the Marshall News Messenger on March, 20, 2011.

Friday, March 4, 2011

Cold Winter Helped...Salvinia Expected To Recover

We've been fortunate this winter to have had a series of cold spells that knocked back the giant salvinia a great deal. It's expected that much of the dead, brown material that is floating will take several weeks to sink out of sight.
Despite this cold weather, we've found several very thick mats around the lake that show survival of green material under the insulating top layer. It's anticipated that these spots will be major expansion points as summer approaches. The first two pictures show the freeze damaged salvinia with green material showing through. These areas should provide good weevil sites for our early season stockings.

On another note, in late February, we completed the re-filling of our weevil tanks with Caddo Lake water. With the warm, sunny weather we've been experiencing lately, the giant salvinia in these tanks has been greening up nicely. Hopefully, our weevils will flourish and be ready for placement on the lake in the very near future!

Finally, here is a recent article about the Caddo Lake salvinia project in the Winter 2011 edition of "TX H2O":

Friday, February 25, 2011

Caddo Lake Giant Salvinia Meeting - April 7, 2011

The next meeting of the Inter-Agency Giant Salvinia Control Team will take place April 7, 2011 at 1 PM in Karnack, Texas, at the Karnack Community Center. This meeting is will provide a platform for local, state and federal agencies to highlight what they are doing in the fight against giant salvinia and will hopefully foster further coordination between these groups.

More information on the Inter-Agency Giant Salvinia Control Team can be found at:

There will also be a community update meeting for anyone who is interested regarding giant salvinia and other Caddo Lake issues at 6 PM on April 7th, 2011 at the Karnack Community Center.

A meeting agenda will be posted once developed. We look forward to seeing all of you there for the evening update meeting.

Giant salvinia mat in Tar Island, November 2010

Friday, February 18, 2011

Weevil Counting Using Berlese Funnels

These strange looking contraptions with lights on top are known as "Berlese Funnels". For our purposes, these funnels are used to estimate the density of weevils (numbers present per amount of giant salvina) located either on the lake or in our weevil rearing tanks.
To use these funnels, a pre-weighed amount of giant salvinia (fresh weight) is placed into the funnel(s) and the 40watt light bulb is turned on for 24 to 48 hours. The weevils, trying to get away from the drying light, fall through a screen and into a mason jar at the bottom of the funnel. By counting these weevils in the jar, we are able to extrapolate how many salvinia weevils are present in an area
of giant salvinia. Although a trip through the Berlese funnel is fatal for the weevils (there is ethyl alcohol at the bottom of the jars for preservation), their sacrifice is not in vain. The weevil numbers obtained from the funnels can tell us when we have sufficient weevil density to put out on the lake.

The funnels were run during the week of February 14, 2011 using samples from the tanks. Despite the very cold weather we've experienced in January and early February of 2011, we still have lots of weevils alive in three out of the four tanks. The one tank that is showing low weevil numbers never got a good population established. We should be able to restock it with weevils from another tank and get a good crop by the time we're ready to release them on the lake. For control of giant salvinia in a system, it's believe that 60 weevils per kilogram of giant salvinia is needed. However, it's believed that weevils should be released for control once they reach 30 per kilogram. One of our tanks is showing over 50 weevils per kilogram of giant salvinia, thus, the sooner we can get these bugs out on the water, the better. The important thing now is to keep these weevils alive and reproducing until it's time to release them on the lake. All in all, the fact that living weevils are present in the tanks shows that the greenhouses have done their job so far.

Monday, February 7, 2011

Big Green Break / Tar Island Salvinia Coverage Video (Fall of 2010)

This video clip was taken November 2010 during an airboat survey (piloted by the TPWD Jasper aquatic vegetation crew) through a thick giant salvinia infestation on Tar Island / Big Green Break on Caddo Lake. This area is a large cypress break located in the middle of the lake positioned on the Texas and Louisiana border. This is a known problem area and is one of the primary giant salvinia nursery areas on the lake. Giant salvinia typically moves downstream into this protected area from other major infestations. It is hoped that this area will become an important weevil release site at some point in the future.

Sorry about the shaky and wobbly footage...airboats are loud, bumpy, and generally difficult to videotape from when using a small, handheld digital camera borrowed from your wife. Notice that at some points, even the powerful airboat struggles to push through the choking giant salvinia mats.

Refilling Weevil / Giant Salvinia Tanks

We are currently in the process (half-way complete) of replacing the well water in our weevil tanks with actual Caddo Lake water. This water replacement is being done with the help of the Karnack VFD and their pump truck; the guys at the Karnack VFD have been extremely helpful in this project and are much appreciated. Lake water is being pumped from the "Starr Ranch" area of the lake on the shore of Goose Prairie.

The reason that we are converting over from well water to lake water is that the well water chemistry was too far from what giant salvinia prefers. The pH and alkalinity of the well water were such that we could not feasibly change the quality of  the water with the typical peat moss and muriatic acid amendments. As you all know, the water in Caddo Lake seems to be more than hospitable for giant salvinia growth, so this is the route we are going to take from here on out.

In addition to a conducive pH and alkalinity, Caddo Lake water also contains higher levels of essential nutrients and minerals as compared to the relatively sterile well water. Nitrogen and iron are critical giant salvinia growth, especially in the weevil tanks, and the lake water will give the salvinia the boost it needs to grow well in the tanks. When the spring growing season arrives, rapidly growing giant salvinia in the tanks will uptake much of the nutrients thus requiring the addition of supplemental fertilizers.

The well water does have the potential to be used in smaller, movable tubs that will be used for a "salvinia nursery" in order to re-stock the weevil tanks once the weevil-infested material is placed out on the lake. Smaller volumes of water are much easier to amend than our 6,000 weevil tanks are.

Thursday, February 3, 2011

New Sign!!

A bright and shiny new sign for the Salvinia Weevil Rearing Facility was installed just outside of greenhouses at the Caddo Lake National Wildlife Refuge in Karnack, Texas. The sign is easily visible from the refuge visitor's center and will help to provide information about the weevil and its impacts on giant salvinia. This sign summarizes the project goals along with the biology of the salvinia weevil. If you're in the area, feel free to come to the main office located near the greenhouses and ask for a tour of the facility.

The Salvinia weevil rearing facility has also gotten some local press in the past week. February 2nd of every year is celebrated as World Wetlands Day and during this year's local celebration, an update on the activities going on with the salvinia weevil rearing facility was a part of the discussion. You can read the article from the
Marshall News Messenger regarding World Wetlands Day on Caddo Lake featuring the Caddo Lake Giant Salvinia Project at:

Also, please visit our frequently updated facebook page. From facebook ,you can search "caddo lake" or simply click the link below.!/pages/Caddo-Lake-Giant-Salvinia-Eradication-Project/162588863767594

Sunday, January 30, 2011

Caddo Lake Weevil Overwintering Study

Beginning in early fall of 2010, a study to document how well salvinia weevils (Cyrtobagous salviniae) can tolerate a Caddo Lake winter was designed by research entomologist Dr. Allen Knutson of the Texas AgriLife Extension Service . To do this, fifty "weevil cages" were built and placed in a densely infested area of giant salvinia in the backwaters of Caddo Lake. In each cage, exactly ten weevils were placed along with a clump of green giant salvinia for them to feed upon. In addition, temperature loggers are recording the surface water temperature at the cage location.

Every two weeks, from fall till early spring, four cages are removed and taken to a lab where the cages are searched for the ten weevils. Alive and dead weevils are counted and recorded to give a complete picture of weevil mortality coinciding with the changing water temperature through winter. Preliminary results show that weevil survival was high until the last week of December 2010 when overall survival plummeted (likely due to the first major cold spell of the winter season). At the end of the study, we'll be able to match the temperature logs with the weevil count data. Results and findings will be published on this blog and the facebook page.

Our next study will use these same cages to monitor the date and temperature in which weevils start laying eggs during a Caddo Lake spring.

So, if you're in the backwaters of Caddo Lake and you see numerous pink, floating styrofoam squares (with wedding veil tulle coming off the top of each square), don't throw it away because it's probably not trash! (or at least not yet)

Saturday, January 29, 2011

Small-Scale Weevil Release on Caddo (Sept. 2010)

This past September 2010, approximately 1,000 salvinia weevils were released into a designated are for research purposes. Weevils were raised at the Lewisville Aquatic Ecosystem Research Facility (LAERF). On a side note, we were totally unprepared for the mud and muck that is Caddo Lake's bottom. The stains did wash out of my jeans, but the Caddo Lake aroma is still there. We now have several good pairs of chest waders to tackle the lake with.

Three months later, in December 2010, area was sampled to see if weevils persisted through the initial cold weather of the season. Out of the twelve hand-sized samples, ten living weevils were found alive. That's not that many, but very encouraging that some living weevils were actually found! The area will be sampled again in mid-February to see if any weevils can be found after the series of cold snaps the region has experienced in January and February of 2011.

Friday, January 28, 2011

Blog and Facebook page online for the Caddo Lake Giant Salvinia Eradication Project

We're online!! The Caddo Lake Giant Salvinia Eradication Project is now being prominently displayed on the web. With the addition of this blog and a new facebook page up and running, we hope to better spread the word to the masses about the efforts to kill giant salvinia at Caddo Lake. If you are reading this, then you know how to get to the blog. You can look us up on facebook by searching for "Caddo Lake Giant Salvinia Eradication Project." You can probably find us just by searching for Caddo Lake, but you never know.

If you have been by the Caddo Lake National Wildlife Refuge lately, you may have noticed two really big greenhouses out behind the headquarters. These greenhouses are being used to grow giant salvinia and salvinia weevils year round so that live weevils can be released on Caddo Lake early this spring while giant salvinia is still recovering from the winter.

Each greenhouse has 2 large tanks inside that are 15ft x 48 ft and hold about 6,000 gallons of water. The Karnack Volunteer Fire Department has been great and helped us out with obtaining water from Caddo Lake to fill these tanks. Believe it or not, giant salvinia is actually hard to grow. It just so happens that it really likes the conditions in Caddo Lake.

Salvinia weevils (Crytobagous salviniae) are a biological control agent used to kill giant
salvinia. The weevils currently being grown at this facility will be released on to Caddo Lake this spring providing a cost effective mechanism for controlling giant salvinia in those parts of the lake that are off the beaten path.

The weevils themselves are tiny little critters that are barely longer than 2 millimeters or about the width of 2 pennies stacked together. The weevils feed on and lay their eggs in giant salvinia causing damage to the plant. When the eggs hatch, the larve eat their way out of the plant causing further damage to the plant and its eventual demise.

So now that you know what is going on in those greenhouses, stop by the main office and ask for Patrick. If he is there, he will be glad to give you a tour.

Don't forget, you can also check out the project website at: