Wednesday, April 9, 2014

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.

Wednesday, April 2, 2014

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

They also have some YouTube video to help explain what they are doing. Check it out below.

Friday, November 22, 2013

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

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.

Thursday, November 7, 2013

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)

Friday, October 18, 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!