Acute toxicity of sodium chloride to first and fourth instar Aedes albopictus larvae

Abstract

The increase in the number of imported cases of dengue fever in Japan is of particular concern as Aedes albopictus is a vector of dengue fever. Due to the potential for insecticide resistance and the impact of insecticides on non-target species, increased attention is being paid to alternative methods of pest control. Placing salt in used tires has been recommended by the Ministry of Health, Labor and Welfare in Japan as a means of controlling mosquitoes. However, the effectiveness of salt as a larvicide against Ae. albopictus are currently unclear. This study examined the acute toxicity of sodium chloride against first and fourth larval instars of Ae. albopictus. Acute toxicity tests were conducted according to World Health Organization guidelines. The susceptibility of Ae. albopictus larvae was tested against 0.25%, 0.5%, 0.75%, 1.00%, 1.25% and 1.5% NaCl solutions. Larval mortality was correlated with an increase in NaCl concentration and exposure duration. First instar Ae. albopictus larvae were more sensitive to NaCl than fourth instar, and 72-h LC₉₀ values for first and fourth larval instars were 0.49% and 1.01% NaCl, respectively. Our results suggest that the application of 0.5% NaCl to a habitat for 3 days is effective for Ae. albopictus control.