A pilot study testing a natural and a synthetic molluscicide for controlling invasive apple snails (Pomacea maculata)

Authors: OLIVIER, HEATHER - Wetlands Research Centre; JENKINS, JILL - Wetlands Research Centre; Berhow, Mark; CARTER, JACOBY - Wetlands Research Centre

Submitted to: Bulletin of Environmental Contamination and Toxicology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/25/2015
Publication Date: 12/21/2015
Citation: Olivier, H.M., Jenkins, J.A., Berhow, M., Carter, J. 2015. A pilot study testing a natural and a synthetic molluscicide for controlling invasive apple snails (Pomacea maculata). Bulletin of Environmental Contamination and Toxicology. 96(3):289-294.

Interpretive Summary: The spread of invasive species threatens the survival of wetland communities. Economic losses caused by invasive species are high, whether generated through direct effects on agriculture or indirect effects via reductions in biodiversity or ecosystem services. By the early 1980’s three non-native snail species were sold or traded as pets in the U.S. These species subsequently escaped and established populations in eleven states. The apple snail is the most widely introduced of the three, with documented populations in Alabama, Arizona, Georgia, Louisiana, Florida, Mississippi, Puerto Rico, North Carolina, South Carolina and Texas as of 2015. As apple snails continue to spread, tools will be needed to control their populations. An integrated pest management approach is one whereby multiple coordinated approaches are used for maximum effect at minimum cost or ecological impact. In this study, we tested chemical control options by comparing two molluscicides, one natural and one synthetic, for their effectiveness on apple snail and on potential biological control species. In this study, adult snails and egg masses were exposed to a saponin-containing tea seed derivative (TSD) and niclosamide, and mortality was recorded. Two non-target species that could serve as biocontrol agents (red swamp crayfish and redear sunfish) were also exposed. Our primary question was which pesticide and concentration was effective at killing the snails without harming non-target species.

Technical Abstract: Pomacea maculata (formerly P. insularum), an apple snail native to South America, was discovered in Louisiana in 2008. These snails strip vegetation, reproduce at tremendous rates, and have reduced rice production and caused ecosystem changes in Asia. In this study snails were exposed to two molluscicides, a tea (Camellia sinensis) seed derivative (TSD) or niclosamide. Mortality was recorded after exposure to high or low concentrations (0.03 g/L and 0.015 g/L for TSD, 1.3 g/L and 0.13 g/L for niclosamide). The TSD induced 100% mortality at both concentrations. Niclosamide caused 100% and 17% mortality at high and low concentrations respectively. These concentrations were also tested on potential biocontrol agents, the red swamp crayfish (Procambarus clarkii) and redear sunfish (Lepomis microlophus). No crayfish mortalities occurred at either concentration for either chemical, but sunfish experienced 100% mortality with TSD (0.03 g/L), and 21% mortality with niclosamide (0.13 g/L).