Biological Control of Salvinia minima at the Barataria Preserve

Tipping, Philip

Common salvinia (Salvinia minima) is one of the most widespread, non-native invasive species at the Barataria Preserve and currently infests more than 9,000 acres, including hundreds of acres of forested swamp habitat and 30 miles of navigable waterways. The salvinia weevil (Cyrtobagous salviniae) has proven to be an effective and safe biological control agent in Florida, where it has become naturalized and is currently widespread on S. minima. Weevils were field collected in Florida off S. minima, checked for pathogens, and then released in experimental sites beginning in June 2002 through June 2005. A total of 9,670 adult C. salviniae were released during the course of the project. Sites were visited a total of 14 times and a variety of biotic and abiotic data captured. Heavy shade was found not to favor weevil establishment so research in heavily shaded sites was discontinued halfway through the project. Full sun sites promoted weevil recoveries and S. minima growing within these sites experienced increased damage. A field nursery site was established at an undisturbed location in Twin Canals in June 2003 and stocked with 2,421 weevils released periodically until August 2005. Although weevil recoveries, including teneral adults, were made at all but one release site during the course of the project, we were unable to determine if establishment occurred as a result of multiple perturbations culminating in Hurricane Katrina at the end of the project. However, damage to plants was minimal and localized in release sites. If C. salviniae did establish, it was present at very low, difficult to detect levels and is most likely to be found in the relatively protected nursery site in Twin Canals. Once this species is established it should constrain the growth of S. minima in full sun locations as seen in Florida. Recommendations for monitoring and integrating biological control with other management approaches are presented herein.

Biological Control of Salvinia minima at the Barataria Preserve

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