Insecticidal Activity of Essential Oils from Syzygium aromaticum and Foeniculum vulgare Var. dulce and Their Major Compounds Against Spodoptera frugiperda and Physiological Selectivity for Trichogramma pretiosum

Spodoptera frugiperda (Lepidoptera: Noctuidae) causes significant losses in major crops and is mainly controlled with chemical insecticides and genetically modified plants; however, improper use of these strategies has led to the development of resistant populations. We evaluated the insecticidal activity of essential oils (EOs) and major compounds of Syzygium aromaticum (Myrtaceae) and Foeniculum vulgare var. dulce (Apiaceae) against S. frugiperda, and their selectivity toward Trichogramma pretiosum (Hymenoptera: Trichogrammatidae). EOs and major compounds were topically applied to caterpillars using a microsyringe. Chromatographic analysis revealed that the major compounds of S. aromaticum were eugenol (76.2%) and (E)-caryophyllene (19.9%), while (E)-anethole (83.35%) was the major compound of F. vulgare var. dulce. The EOs of S. aromaticum and F. vulgare var. dulce were toxic to S. frugiperda (LD50 = 54.2 and 41 µg/caterpillar, respectively), compared with 0.03 µg a.i./caterpillar for chlorpyrifos, with (E)-anethole accounting for most of its insecticidal activity. The EOs also adversely affected larval development, fecundity, and life table parameters. Additionally, the EO of S. aromaticum was harmful to adult T. pretiosum females, whereas F. vulgare var. dulce EO and (E)-anethole were harmless to slightly harmful to the parasitoid’s immature stages, highlighting their potential for selective control of S. frugiperda.