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

Abstract

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.

Keywords: Phthorimaea absoluta; Bioinsecticide; Miridae; Nanotechnology; Side effect; Two-sex life table.

Fig. 1

GC–MS chromatogram of Foeniculum vulgare seeds essential oil with identified peaks listed in Table 1.

Fig. 2

Physical properties of Foeniculum vulgare essential oil-loaded nanostructured lipid carrier (FVO-NLC): (a) scanning electron microscope (SEM) micrograph, (b) particle size, (c) zeta potential distributions profile, (d_i) FTIR spectra of FVO-NLC and nanostructured lipid carrier without FVO (Control NLC), (d_ii) FTIR spectra of FVO-NLC and Control NLC in expanded form in the range 1600–1000 cm⁻¹, and (d_iii) in the range 1800–1600.

Fig. 3

Survival rate by age-specific stage (Sxj) of Phthorimaea absoluta in (a) Foeniculum vulgare pure essential oil (FVO), (b) trans-anethol (TAL), (c) FVO-loaded nanostructured lipid carrier (FVO-NLC), and (d) control (There was no significant difference between NLC sample prepared without FVO loading and distilled water–ethanol mixture, as controls).

Fig. 4

Life expectancy by age-stage (Exj) of Phthorimaea absoluta in (a) Foeniculum vulgare pure essential oil (FVO), (b) trans-anethol (TAL), (c) FVO-loaded nanostructured lipid carrier (FVO-NLC), and (d) control (There was no significant difference between NLC sample prepared without FVO loading and distilled water–ethanol mixture, as controls).

Fig. 5

Survival rate by specific age-stage (lx), fecundity by specific age-stage (Fx, female), fecundity by specific age (mx), and maternity by specific age (lxmx) for Phthorimaea absoluta in (a) Foeniculum vulgare pure essential oil (FVO), (b) trans-anethole (TAL), (c) FVO-loaded nanostructured lipid carrier (FVO-NLC), and (d) control (There was no significant difference between NLC sample prepared without FVO loading and distilled water–ethanol mixture, as controls).

Fig. 6

Reproductive value by age-stage (vxj) of Phthorimaea absoluta in (a) Foeniculum vulgare pure essential oil (FVO), (b) trans-anethole (TAL), (c) FVO-loaded nanostructured lipid carrier (FVO-NLC), and (d) control (There was no significant difference between NLC sample prepared without FVO loading and distilled water–ethanol mixture, as controls).

Fig. 7

The persistence of contact toxicity of trans-anethole (TAL), Foeniculum vulgare pure essential oil (FVO), and FVO-loaded nanostructured lipid carrier (FVO-NLC) against Phthorimaea absoluta second instar larvae at the highest concentration (LC₉₅) for different periods.