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.