As with other organophosphates, temephos affects the central nervous system through inhibition of cholinesterase. In larvae, this results in death before reaching the adult stage.
Resistance to temephos by A. aegypti has been seen in Brazil. The Brazilian Aedes aegypti resistance monitoring program detected temephos resistance in A. aegypti populations from several localities in the country in 1999 (Funasa 2000, Lima et al. 2003). In 1999, mosquitoes from the city of Rio de Janeiro were observed to be resistant to temephos.[5]