ABSTRACT
Aerial applications of liquid methoprene are used in salt marshes to control mosquitoes by preventing adult emergence. Despite concern about toxicity to non-target organisms, little is known about environmental concentrations after applications, nor methoprene's persistence in salt marsh environments. Aqueous and sediment samples were collected from two marshes receiving weekly applications. Aqueous samples were collected as early as 30â¯min after applications and as long as nine days afterwards; sediment samples were taken within hours of application and as long as 19â¯days post-application. Use of time-of-flight liquid chromatography - mass spectral analysis allowed for ultra-low detection limits (0.5â¯ng/L) in water samples. The data show loss of nearly all methoprene from 1â¯m deep marsh ditches within 1â¯day and presence but not accumulation of methoprene in marsh sediments despite repeated applications. Methoprene concentrations observed in salt-marsh mosquito ditches were below those found to be of toxicological significance in other studies.