Weevils versus No Weevils: a Comparison of Salvinia Minima Populations in Florida and Louisiana

Cyrtobagous salviniae Calder and Sands (Coleoptera: Curculionidae) is a successful biological control agent of aquatic weeds suppressing species like giant salvinia, Salvinia molesta D.Mitch. (Salviniales: Salviniaceae), in at least 15 countries over 3 continents (Julien et al. 2002). There are at least 2 ecotypes of this insect; the smaller Florida ecotype found on common salvinia, S. minima Baker, throughout Florida, and the larger Brazil ecotype, which has been used extensively against S. molesta (Jacono 2001). Despite initial questions about the identity of the Florida ecotype (Goolsby et al. 2000), molecular work has confirmed that the 2 ecotypes represent a single species (Madeira et al. 2006). Although S. minima causes significant problems in Louisiana, it rarely forms persistent mats in Florida (Tipping et al. 2012). This regional difference may be caused by herbivory by the Florida weevil ecotype, which was first reported in Florida in 1962 (Kissinger 1966). The goal of this study was to compare population variables of S. minima between freshwater swamp forest habitats located in different states where one (Louisiana) lacks C. salviniae. Generalist herbivores like Synclita oblteralis (Walker) (Lepidoptera: Crambidae) and Samea multiplicalis Guenée (Lepidoptera: Crambidae) are present on S. minima in both states (Munroe 1972; Knopf and Habeck 1976). Environmental, plant, and insect variables were compared between 4 field sites in Florida and 5 in Louisiana during 11 dates between 2002 through 2004. Florida sites were located near Immokalee, West Palm Beach, and LaBelle while Louisiana sites were located within the Barataria preserve south of New Orleans. In Florida,