Abstract: Insecticide resistance (IR) in mosquitoes continues to increase, making effective control of the most important human vectors difficult throughout the Southern US. Varied resistance intensity is often found within districts and multiple biological mechanisms are responsible for resistance to different pesticide classes. In Aedes aegypti, the knock down resistance (kdr) gene mutations have been found to be indicative of pyrethroid resistance in populations from Florida, Texas, Arizona, California, Mexico and Peru. When kdr is the primary underlying IR mechanism, testing dead or live samples by allele-specific PCR provides a cheap, fast, and highly predictive method to determine a susceptibility to pyrethroids. These data, when compared to kdr genotype specific field efficacy studies, will then determine if the pyrethroid formulation will be effective, or if switching to another active ingredient, such as an organophosphate, is necessary to produce high mortality. In other species, like Culex quinquefasciatus, where enzymatic mechanisms are the major IR factor, wind tunnel tests using local mosquitos can provide data on the efficacy of field sprays of formulated product. If adulticide testing proves to be ineffective due to a local mosquito population’s IR mechanism(s), efforts can then be put into controlling other life stages, i.e. treating larval habitats with microbial larvicides or insect growth regulators. As IR is most pronounced on efforts to control adult mosquitoes, determining which formulations are most effective for local populations is crucial to avoid further intensification of IR and the distribution of ineffective chemicals to the environment. This can only be accomplished if IR, and the mechanisms involved, are assessed regularly, and then these data are used to inform control efforts.
