Toxicity of Nanoemulsified Eugenia uniflora (Myrtaceae) Essential Oil to Spodoptera frugiperda (Lepidoptera: Noctuidae) and Selectivity to Trichogramma pretiosum (Hymenoptera: Trichogrammatidae)

<i>Spodoptera frugiperda</i> (fall armyworm) is a polyphagous pest with widespread resistance to synthetic insecticides, while essential oils (EOs) and biological control agents, such as the parasitoid <i>Trichogramma pretiosum</i>, represent promising strategies in integrated pest management (IPM) programs. This study evaluated the toxicity of <i>Eugenia uniflora</i> EO, popularly known as pitanga EO, and nanoemulsion (NEO) to <i>S. frugiperda</i> and the selectivity of the NEO to <i>T. pretiosum</i>. The EO of <i>E. uniflora</i> was characterized by GC-MS/DIC and then diluted in water and Tween 80^® for bioassays to estimate the LC₅₀ against <i>S. frugiperda</i> in Potter's tower. The NEOs were produced by high-shear dispersion using an Ultra-Turrax and characterized for thermal stability, particle size, polydispersity index (PDI), zeta potential (ζ), temporal stability, and morphology. The NEO was diluted to the LC₅₀ (36.05 mg/mL) in 1% Tween 80^® solution and tested for toxicity to <i>S. frugiperda</i> and to the parasitoid. The majority compounds in the EO from <i>E. uniflora</i> were curzerene (34.07%), selina-1,3,7(11)-trien-8-one (10.51%), germacrene B (9.51%) and germacrene D (5.03%). The NEO stored at 25 °C remains stable for up to 30 days after preparation. In addition, the NEO showed a particle size of 283.2 nm, a PDI of 0.289, and a zeta potential (ζ) of -23.2 mV. The <i>E. uniflora</i> EO and NEO at a concentration of 36.05 mg/mL were toxic to <i>S. frugiperda</i> (36% probability of survival). Furthermore, NEO was selective for <i>T. pretiosum</i> in its immature stages. The NEO proved to be stable, effective, and selective, indicating potential for IPM. However, validation under semi-field and field conditions is still necessary.