Physiological and molecular responses of house fly (Musca domestica L.) to clove flower bud extracts

The house fly, Musca domestica, is a major mechanical vector of several pathogens, posing significant public health risks. Due to the hazards associated with indoor use of synthetic insecticides, biopesticides offer an eco-friendly alternative. Clove (Syzygium aromaticum) flower bud extract contains bioactive insecticidal compounds; however, a comprehensive study of its sublethal effects on M. domestica, along with the associated molecular responses, was lacking. Ethanol-based clove extracts were characterized using gas chromatography-mass spectrometry (GC-MS). This study assessed the lethal and transgenerational effects of clove extract on two generations using age-stage, two-sex life table analysis. Gene expression analysis was conducted on three key stress-responsive genes (CYP12A2, CYP6D2, CYP6A24) and one fecundity-related gene, vitellogenin-I (Vg-I). GC-MS analysis identified eugenol (68.80%), caryophyllene (13.24%), and acetyl eugenol (13.56%) as the major constituents. The lethal concentrations were determined as LC₅ = 0.405%, LC₅ = 1.574%, and LC₅₀ = 4.046%. The LC₅₀ treatment significantly reduced longevity, fecundity, and survival. Mean generation time (T) was significantly shorter in the LC₅₀ group (16.43 days) than in the control (19.89 days). Similarly, key population parameters-intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R₀)-were reduced. Gene expression studies revealed elevated stress responses and reproductive suppression. The detoxification genes (CYP12A2, CYP6D2, CYP6A24) were upregulated, while the fecundity-related gene Vg-I was downregulated. Molecular docking suggested strong binding affinity of caryophyllene to survival-related proteins. These findings suggest that clove extract significantly affects M. domestica, highlighting the potential of caryophyllene as an insecticidal compound.