Toxicity of Foeniculum vulgare essential oil, its main component and nanoformulation against Phthorimaea absoluta and the generalist predator Macrolophus pygmaeus

The encapsulation of essential oils (EOs) in nanostructured lipid carriers (NLCs) represents an innovative and advanced approach to improve their stability and efficacy. This study evaluated, for the first time, the toxicity of Foeniculum vulgare EO (FVO), its main component, and nanoformulation (FVO-NLC) on Phthorimaea absoluta and their side effects on generalist predator, Macrolophus pygmaeus. The obtained FVO-NLC had spherical and small (86.32 nm) particle sizes, and its encapsulation efficacy was greater than 98%. FTIR analysis revealed no significant chemical interaction between EO and NLC components. Trans-anethole (TAL) (66.22%) was identified as the key FVO component. The leaf dip method was used for bioassays. FVO-NLC and FVO showed a similar level of contact toxicity against P. absoluta with LC₅₀ values of 5.57 and 5.44 µL/mL, respectively, while TAL had an LC₅₀ value of 3.93 µL/mL. The lethality test revealed the slow and persistent release of FVO from FVO-NLC. Furthermore, the life table data were analyzed using the TWO SEX-MSChart program. Results indicated that all selected bio-insecticides at their LC₅₀ values reduced fecundity and negatively affected biological and population growth parameters in target pest, and usage of them was proved to be harmless for the predator according to IOBC protocols.