ABSTRACT. Cyrtobagous salviniae is widely used in several countries including the United States, South Africa and Australia for biological control of Salvinia molesta Mitchell (Salviniales: Salviniaceae). Despite considerable success in tropical and subtropical regions, the effectiveness of C. salviniae on S. molesta is inconsistent in temperate regions, indicating the need for populations adapted to cooler climates. The objectives of this study were to determine the regions of South America that are climatically similar to S. molesta habitats in temperate Louisiana, conduct surveys for new provenances of C. salviniae in these regions, establish the phylogenetic relationships among C. salviniae provenances, and compare the cold tolerance of populations of C. salviniae from Louisiana, USA and the Lower Paraná-Uruguay Delta (LPUD), South America. Foreign exploration of the Lower Paraná-Uruguay Delta region resulted in the first record of C. salviniae in Uruguay, and revealed the most southern distribution of this species in Argentina and Uruguay. Phylogenetic identification of this provenance indicated that it is a different biotype to the one from Brazil which was first released in the United States in 2001. Analysis of the climate in south, central, and north Louisiana revealed colder and more frequent cold fronts in the north, likely contributing to winter population crashes. Regional differences in Louisiana thermal regimes indicate that there is a need for region specific management plans, such as the inclusion of cold tolerant C. salviniae populations in the management of S. molesta in temperate regions. The cold tolerance of C. salviniae populations from Louisiana and Lower Paraná-Uruguay Delta were compared by measuring survival at 0 °C, chill coma recovery times, and supercooling points (SCP). Survival at 0 °C was 1.5-times greater, mean chill coma recovery time was 1.8-times faster, and mean SCP was 1.2-times lower in the Lower Paraná-Uruguay Delta population compared to the Louisiana population. These findings show that the Lower Paraná-Uruguay Delta provenance should be considered for managing S. molesta in temperate regions. Besides host range tests on the Lower Paraná-Uruguay Delta biotype, cross breeding between the Louisiana and Lower Paraná-Uruguay Delta populations of C. salviniae should be investigated to determine the life histories of any possible hybrids. 2017 Elsevier Inc. All rights reserved.