Lethal and sublethal effects of fluralaner (isoxazoline) on the biology of the house fly, Musca domestica L. (Diptera: Muscidae)

Background Fluralaner, a novel isoxazoline insecticide, has demonstrated potential to control Musca domestica ; however, its lethal and sublethal effects on the biology of this species remain unknown. Here, we evaluated lethal and sublethal effects of fluralaner on the biological traits and population parameters of M . domestica using the age‐stage, two‐sex life table model. Results Topical bioassays revealed LD 10 , LD 20 , and LD 50 values (representing 10%, 20%, and 50% mortalities) of 0.42, 0.63, and 1.35 ng fly −1 , respectively, for females, and 0.33, 0.50, and 1.09 ng fly −1 , respectively, for males of M . domestica . Exposure of adults to these concentrations induced significant, dose‐dependent negative effects on reproductive performance, preadult development, adult longevity, and the survival of different stages. All immature stages were prolonged, with total preadult duration increased from 11.26 days in controls to 15.32 days at LD 50 . Fecundity declined sharply from 428.66 eggs per female in controls to 297.23 eggs at LD 50 , whereas preadult survival rate decreased from 0.88 to 0.57. Population growth parameters also reflected these effects: the intrinsic rate of increase ( r ) and finite rate of increase ( λ ) were significantly reduced at LD 20 and LD 50 , and the net reproductive rate ( R 0 ) decreased with increasing concentrations of fluralaner. Mean generation time ( T ) was prolonged in all treated groups, reaching 30.59 days at LD 50 . Life expectancy ( e xj ) and reproductive values ( v xj ) were also adversely affected, with peak reproductive output delayed from 25 days in controls to 33 days in the LD 50 treatment. Conclusion The data in the current study demonstrate that fluralaner, even at sublethal concentrations, can suppress M . domestica population growth through lengthened development and weak reproductive performance. The results provide a baseline for using fluralaner in M . domestica management programs, with due consideration of its sublethal effects on population dynamics.