Semester of Graduation

Summer 2023


Master of Science (MS)



Document Type



Giant salvinia (Salvinia molesta Mitchell), an invasive free-floating aquatic fern, invaded the Toledo-Bend reservoir along the Texas-Louisiana border in the 1990s. The rapid spread threatens critical ecosystems, economies, and cultural services by altering water quality, and impacting fishing, hunting, and navigation. To combat this issue, the LSU AgCenter has been rearing and distributing the salvinia weevil (Cyrtobagous salviniae Calder and Sands), which has demonstrated effectiveness in reducing giant salvinia populations within a matter of months to a few years. The first study assessed the impact of propagule pressure on salvinia weevil effectiveness in outdoor mesocosms and revealed that increasing propagule pressure increased plant damage by 40%. A six-month outdoor pond study revealed that adult salvinia weevil flight behavior had a positive relationship between higher salvinia weevil density, while a negative relationship was observed with decreased host plant quality. The competitive interaction between giant salvinia and Cuban bulrush (Oxycaryum cubense (Poepp. & Kunth) Lye) and its impact on the salvinia weevil were also investigated. The presence and coverage of Cuban bulrush did not significantly affect salvinia weevil population growth under short-term conditions, which suggest that salvinia weevil should be released even in the presence of Cuban bulrush. Furthermore, the compatibility of triclopyr, an herbicide commonly used to control Cuban bulrush, with the salvinia weevil was examined. The study found that triclopyr had no significant impact on adult salvinia weevil mortality, thus indicating that it can be safely applied to control Cuban bulrush without harming salvinia weevil populations. The findings of this research contribute to the development of an integrated pest management (IPM) program for effective giant salvinia control. By adopting an IPM approach and incorporating the findings of this research, natural resource managers can effectively manage giant salvinia infestations and promote the restoration of impacted freshwater ecosystems.



Committee Chair

Diaz, Rodrigo

Available for download on Wednesday, July 08, 2026