Release and evaluation of Cyrtobagous salviniae on common salvinia in southernLouisiana

摘要

Common salvinia (Salvinia minima) is one of the most widespread, non-native invasive species at the Barataria Preserve of Jean Lafitte National Historical Park and Preserve in southern Louisiana and currently infests more than 3,600 ha and 48 km of navigable waterways. A proven biological control agent, the salvinia weevil (Cyrtobagous salviniae Calder and Sands), was field collected on S. minima in Florida, checked for pathogens, and then released in the Preserve from June 2002 through June 2005. Few weevils were recovered from heavily shaded sites when compared to full sun sites where weevils were recovered frequently. Plant biomass and percent cover were reduced only in full sun sites. 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 weevils, including teneral adults, were recovered at all but one release site, population establishment was not confirmed during this periodbecause of multiple perturbations, culminating in Hurricane Katrina, which caused large scale saltwater intrusion which temporarily destroyed all the sites near the end of the project. However, recent weevil detections by other researchers suggest that the weevils did establish in the area. Any future research efforts in this region should focus on identifying full sun, undisturbed sites to expedite establishment and evaluate impact.