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)

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