Anise (Pimpinella anisum) and fennel (Foeniculum vulgare) essential oils and their combination as natural and safe housefly (Musca domestica) ovicides

Essential oils (EOs) are potential natural substitutes for synthetic insecticides. This study investigated the ovicidal efficacy and environmental safety of single and combined formulations of anise ( Pimpinella anisum ) and fennel ( Foeniculum vulgare ) EOs against the housefly, Musca domestica . For efficacy evaluation, all formulations were stored at 25 °C and their ovicidal activity and stability were assessed after one year, using α -cypermethrin as a standard insecticide control. A 1:1 anise–fennel EO mixture showed the highest activity, achieving complete ovicidal effect (100%) for up to 6 months under laboratory conditions, with LC 50 values of 0.07–0.08 µL egg⁻¹. After one year of storage, the formulation remained highly effective, with 95% inhibition and an LC 50 of 0.08 µL egg⁻¹. The combined formulation exhibited strong ovicidal synergy and was more effective than individual EO formulations and α-cypermethrin at all time points (synergistic inhibition index: 12.9–16.3). Morphological observations of treated eggs revealed damage to the hatching line, aeropyles, and plastron. In a separate safety assessment, toxicity was evaluated using the non-target earthworm Eisenia fetida , where all EO treatments showed no apparent toxicity, while α-cypermethrin was highly toxic. These results demonstrate that the 1:1 combined anise and fennel EO formulation is an effective, stable, and environmentally safe ovicidal agent for sustainable housefly control.