Giant salvinia, Salvinia molesta Mitchell, and common salvinia, Salvinia minima Baker, are free-floating aquatic ferns native to South America that can grow rapidly to cover the surface of lakes and streams. Giant salvinia has caused severe problems in the waterways of 13 countries (including the U.S.) on three continents, while common salvinia can be problematic in areas of the southeastern United States. S. molesta has been controlled successfully first in Australia and then in many other countries through releases of the weevil Cyrtobagous salviniae Calder and Sands. In Florida, a genetically distinct strain of C. salviniae appears to reduce the severity of S. minima infestations. To date, there has been no published comparison of the relative efficacy of each strain in controlling each salvinia species, and the effect of temperature has only been studied for the strain used in Australia. In a factorial experiment with weevil strain, plant species and temperature profile as factors, we examined differences in population growth rates of both weevil strains on both host plants. We also examined the effects of adult and larval feeding in these treatments on the change in biomass of the plants. This information allows us to make recommendations about conditions in which it is appropriate to release each weevil strain against salvinia infestations.
Species 1: Coleoptera Curculionidae Cyrtobagous salviniae
Keywords: biological control, aquatic weeds
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