Doctor of Philosophy (PhD)



Document Type



Common salvinia, Salvinia minima Baker, is a floating aquatic invasive macrophyte that obstructs waterways and causes problems in wetlands across Louisiana and Texas. The salvinia weevil, Cyrtobagous salviniae Calder and Sands, has been released in over 14 countries around the world for the biological control of Salvinia spp. We successfully monitored the introduction and establishment of C. salviniae on S. minima in southern Louisiana between 2006 and 2010. Cyrtobagous salviniae significantly lowered the biomass of S. minima and increased the number of terminal buds damaged but had no significant impact on pH, dissolved oxygen, conductivity, surface temperature, percent of surface coverage, or percent of the mat that was green. Restricting access to the S. minima mat from the red imported fire ant, Solenopsis invicta Buren, significantly increased the number of C. salviniae, suggesting that S. invicta should be controlled where possible to maximize the success of the biological control program. While collecting arthropods associated with S. minima, we identified 5,773 individuals that represent 176 species within 62 families and seven orders including four currently undescribed species, and seven species of semi]aquatic Curculionidae (five of which have been used in biological control programs). We collected higher numbers of taxa than previous studies, but most of the species are previously known as hydro] or hygrophilous, indicating the differences may have been due to collection methods. Collecting locations were clustered into five groups based on secondary aquatic vegetation and evaluated by cluster for community composition and similarity. We found no support for the spatial heterogeneity hypothesis, as our most diverse community is one of the least spatially complex, suggesting other factors are affecting community composition. Findings included successful establishment of C. salviniae, recommendation to control S. invicta around C. salviniae release sites, improved methods for collecting insects associated with floating aquatic vegetation, and contributions to the knowledge of the biodiversity of Louisianafs backwater swamps. In addition to providing new information on interactions between C. salviniae and S. minima, these studies will be useful in designing,evaluating, and monitoring releases of other biological control agents on floating aquatic macrophytes.



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Committee Chair

Johnson, Seth J.

Included in

Entomology Commons