Weevils versus no weevils: A comparison of Salvinia minima populations in Florida and Louisiana

Abstract

Although the range of S. minima in the U.S. includes Florida and Louisiana, the plant behaves differently between states, most notably in Louisiana where it is considered a significant aquatic weed. Plant and insect populations were sampled 11 times in both states over consecutive weeks during 2002 through 2004. Mean S. minima biomass was more than twice as great in Louisiana as compared with Florida. Plant coverage was also greater and plants were healthier in Louisiana. The most unequivocal difference between states was the absence of Cyrtobagous salviniae in Louisiana. This specialist herbivore has repeatedly demonstrated its ability to suppress S. minima and probably accounts for its differential weed status between states.