Comparative susceptibility of larvae of three Aedes species to malathion and permethrin.

Larvae of Aedes hendersoni, Ae. atropalpus, and 6 geographic strains of Ae. triseriatus were compared in terms of their susceptibility to malathion and permethrin. Aedes atropalpus was most tolerant to malathion, whereas Ae. triseriatus (Walton strain) was most tolerant to permethrin. Malathion LC50S for 6 geographic strains of Ae. triseriatus ranked from high to low were: Alabama (ALA) > Michigan (UNDERC) > Indiana (WAL) > Kentucky (UKEN) > Texas (SAL) > Florida (VB); similar ranking of permethrin LC50S resulted in: WAL > VB > SAL > UKEN > UNDERC > ALA. Differences in susceptibility were detected but were not considered large (i.e., over several orders of magnitude). As a result, no change in application rate of malathion or permethrin, from an operational viewpoint, would be warranted if used against these 3 mosquito species or the geographic strains of Ae. triseriatus investigated.