Inheritance patterns of resistance to sodium channel blocker insecticides in Spodoptera frugiperda (Lepidoptera: Noctuidae).

The use of sodium channel blocker insecticides (SCBIs) has been one of the tools for managing the resistance of fall armyworm Spodoptera frugiperda (J.E. Smith, 1797) (Lepidoptera: Noctuidae) to insecticides. In this study, we selected resistant strains of S. frugiperda to the SCBIs indoxacarb (Indoxacarb-R) and metaflumizone (Metaflumizone-R), under laboratory conditions, to evaluate the inheritance of resistance, cross-resistance to insecticides targeting voltage-gated sodium channels, and verify the absence of the F1845Y and V1848I mutations. The LC₅₀ values of the susceptible (SUS) and the Indoxacarb-R strains to indoxacarb were 3.72 and 114.43 µg mL^-1 respectively, and for the SUS and the Metaflumizone-R strains to metaflumizone were 4.57 and 3,141.96 µg mL^-1, respectively, with resistance ratios of approximately 30-fold to indoxacarb and >600-fold to metaflumizone. The resistance of S. frugiperda to both insecticides was characterised as autosomal, incompletely recessive, and polygenic. Cross-resistance between indoxacarb and metaflumizone was detected. Moreover, Indoxacarb-R and Metaflumizone-R strains showed lower susceptibility to the pyrethroid insecticide lambda-cyhalothrin, possibly due to multiple resistance. The partial sequencing of the S. frugiperda sodium channel gene did not confirm the association of F1845Y and V1848I mutations with S. frugiperda resistance to indoxacarb and metaflumizone. These results will be important for implementing proactive insect resistance management programmes to preserve the lifetime of SCBIs in controlling S. frugiperda.