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)

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