Ovipositional Repellency of Fatty Acids and Their Derivatives Against Culex1 and Aedes1 Mosquitoes

Abstract

Lower aliphatic carboxylic acids are known to induce negative ovipositional responses in various species of mosquitoes. Straight-chain higher fatty acids from C₅ to C₁₃ and some of their methyl and ethyl esters and amides were evaluated for ovipositional activity in a laboratory olfactometer system against two species of Culex and one species of Aedes mosquitoes. Of these higher acids, nonanoic acid (C₉) was the most repellent against C. quinquefasciatus and C. tarsalis, demonstrating significant repellency at 1 × 10⁻⁴ M. Nonanoic acid was also the most active acid against A. aegypti, significantly repelling the ovipositing mosquito at as low as 1 × 10⁻⁵ M. Some of the higher acids, such as C₈, C₉, and C₁₀ acids, were as active as, or more active than, the lower acids from C₂ to C⁶ against these three species of mosquitoes. Among the methyl and ethyl esters of C₈ to C₁₀ acids, only ethyl nonanoate showed considerable repellency. The amides of C₈ to C₁₀ acids did not exhibit any activity.