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!

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