Abstract Mosquito-borne diseases remain a major challenge in global public health. Larval management is an important strategy for mosquito control, yet few chemical classes of insecticides are available that target larvae. Moreover, resistance to adulticides can translate to resistance in both adults and larvae, further reducing effective control options. Consequently, there is a need to identify novel insecticides with new modes of action (MoA) that can circumvent existing resistance while maintaining favorable human and animal safety profiles. Isoxazolines and meta-diamides represent relatively new chemical classes of insecticides, with distinct MoA and the added benefit of a favorable mammalian toxicity profile. This study evaluated the comparative toxicity of the isoxazolines afoxolaner, fluralaner, fluxametamide, and the meta-diamide broflanilide against Aedes aegypti (Linnaeus 1762). (Diptera: Culicidae), Anopheles quadrimaculatus (Say 1824) (Diptera: Culicidae), and Culex quinquefasciatus (Say 1823) (Diptera: Culicidae) larvae. These species represent significant vectors and are commonly used in efficacy testing toward EPA registrations of mosquitocides. Across all three species, fluralaner was the most toxic, being over 290- to 690-fold more toxic than spinosad, a commonly used mosquito larvicide. Anopheles quadrimaculatus was the least sensitive to all insecticides, however, the isoxazolines and broflanilide were still more toxic than spinosad. In susceptible Cx. quinquefasciatus, fluralaner was over 1000-fold more toxic compared to spinosad. Limited cross resistance, up to 2.5-fold and 5.3-fold, was observed in a pyrethroid resistant strain of Ae. aegypti and a multi-insecticide resistant strain of Cx. quinquefasciatus, respectively. These results indicate that isoxazolines and meta-diamides warrant further consideration as mosquito larvicides.
Dagg et al. (2026) studied this question.