Toxicity of emulsions, high and low energy nanoemulsions of orange essential oil and d-limonene to Drosophila suzukii, and selectivity to Pachycrepoideus vindemmiae

Abstract Sweet orange essential oil ( Citrus sinensis ) and its major component d -limonene were formulated as emulsions and low- and high-energy nanoemulsions and evaluated for toxicity against adults, larvae, and pupae of Drosophila suzukii , as well as for selectivity toward the pupal parasitoid Pachycrepoideus vindemmiae . High-energy nanoemulsions produced smaller and more homogeneous droplets (221–289 nm; PDI 0.210–0.255) compared with low-energy nanoemulsions (617–796 nm; PDI 0.548–0.644), indicating improved dispersion and potential stability. Toxicity assays revealed that the pure essential oil and d- limonene were the most toxic to adult D. suzukii (LC 50 = 1.7 wt% and 0.54 wt%, respectively), followed by high-energy nanoemulsions, emulsions, and low-energy nanoemulsions. Although pure compounds showed slightly higher toxicity, high-energy nanoemulsions maintained comparable efficacy, suggesting improved delivery without major loss of activity. Larval mortality did not exceed 40% across treatments, whereas pupae were markedly more susceptible. High-energy nanoemulsions of both orange essential oil and d -limonene produced the highest pupal mortality (around 85%), followed by low-energy nanoemulsions (72–77.5%) and emulsions (50–75%). In addition, emulsified and nanoemulsified formulations induced developmental abnormalities in emerged adults, with malformation rates reaching 30%. Selectivity assays demonstrated low toxicity of all formulations to adult P. vindemmiae , with mortality generally below 20% and a negligible reduction of parasitism activity in most treatments. Overall, the formulation method strongly influenced physicochemical properties and insecticidal performance. High-energy nanoemulsions enhanced efficacy, particularly against pupae, while maintaining low toxicity to a key parasitoid. These findings indicate that nanoformulated citrus essential oils represent promising selective and environmentally compatible tools for integrated management of D. suzukii .