An Experimental Evaluation of Toxicity Effects of Sodium Chloride on Oviposition, Hatching and Larval Development of Aedes albopictus

Abstract

Dengue virus, one of the most important mosquito-borne viruses, has shown a sharp upward trend, spreading around the world in recent years. Control of vectors Aedes aegypti and Ae. albopictus remains crucial for blocking dengue transmission. The lethal ovitrap (LO) is one of the cost-effective traps based on the classic “lure and kill” strategy, and finding a proper long-lasting effective toxin is key to achieving the desired effect. The concentration of inorganic salts of habitat environment plays a strong role in affecting oviposition, hatching, and development of mosquitoes, but the potential insecticide activity of Sodium Chloride (NaCl) in habitat water as well as LO still lacks research. In this study, we carried out laboratory experiments to systematically explore the effects of different concentrations of NaCl solutions on oviposition, egg hatching, and larval development of Ae. albopictus. Consequently, Ae. albopictus was found to prefer freshwater to lay eggs; whereas 48.8 ± 2.6% eggs were laid in freshwater and 20% in ≥1.0% brackish water, few eggs were laid in 3.0% NaCl solution. Compared with egg hatching, larval development of Ae. albopictus presented a higher sensibility to NaCl concentration. The mortality of the 3rd–4th larvae in 1.0% NaCl solution was 83.8 ± 8.7%, while in 3.0% it reached 100%. Considering the cumulative effect of NaCl, when NaCl concentration was ≥1.0%, no eggs could successfully develop into adults. These data suggested that NaCl solutions with a concentration ≥1.0% can be used as an effective cheap insecticide for Ae. albopictus in subtropical inland aquatic habitats, and also as the “kill” toxin in LOs. Meanwhile, the concentration range from 0 to 2.0% of NaCl solution has the potential to be used as the “lure” in LOs. The technological processes of how to use NaCl as insecticide or in LOs still needs further in-depth exploration.