Synthetic insecticides are widely used against mosquitoes, but misuse has led to environmental and health concerns. Plant-derived alternatives, such as essential oils, seem to offer a safer option, minimizing these problems without compromising efficacy. In this study, we evaluated the essential oil from Siparuna gesnerioides (Kunth) A.DC., a Neotropical plant, for its effectiveness in controlling Aedes (Stegomyia) aegypti (Linnaeus) larvae, a major vector of human diseases. We first assessed the phytochemistry of the essential oil and used in silico approaches to predict potential physiological targets of its larvicidal activities. Selectivity assays were conducted with Belostoma anurum (Herrich-Schäffer), a non-target predatory water bug. The major constituents of S. gesnerioides essential oil were γ-elemene (45.8%) and germacrene D (43.8%). This essential oil effectively killed larvae from both susceptible and resistant mosquito strains (LC50 = 0.070 μg/mL). However, such concentrations killed more than 80% of B. anurum nymphs. Molecular modeling suggested that the essential oil major components (γ-elemene and germacrene D) interact stably with mosquito acetylcholinesterases (AChEs), indicating a potential mechanism of action. Our results reinforce the potential of Siparuna essential oils in mosquito control. Nevertheless, the non-selective impact on mosquito predators, as seen with S. gesnerioides, highlights the need for caution in field applications.

Essential oils obtained from Siparuna plants, e.g., S. guianensis and S. gesnerioides, have potential for use as biorational insecticides. However, the activities of S. gesnerioides oils remain largely unexplored compared to S. guianensis oils. Using an integrative approach combining toxicological bioassays, geometric morphometrics, and in silico modeling, we assessed the adulticidal potential, selectivity, and the effects of early-life exposure to these oils on the larval susceptibility and adult wing morphometry of Aedes aegypti. Adulticidal assays revealed high toxicity, with S. guianensis (LC₅₀ = 15.0 nL/mL) being 15-fold more potent than S. gesnerioides (LC₅₀ = 233.0 nL/mL). Beyond acute lethality, early-life (i.e., eggs to L2 larvae) exposure to sublethal concentrations (S. guianensis = 7.4 nL/mL and S. gesnerioides = 118.0 nL/mL) was associated with wing morphometric disruptions and increased fluctuating asymmetry in Ae. aegypti adults, especially in those exposed to S. gesnerioides essential oil. Furthermore, early-life exposure to S. gesnerioides modulated L4 larvae susceptibility, which was associated with lower mortality in subsequent exposures. Selectivity assays demonstrated low acute oral toxicity in initial laboratory screenings with Apis mellifera, while molecular docking approaches predicted higher affinity of bicyclogermacrene and α-copaene for Ae. aegypti TRPV channels. Collectively, while S. gesnerioides oil was less acutely toxic, early-life sublethal exposures reduced fourth instar larvae (L4) susceptibility, which may have contributed to developmental instability and morphological alterations in adults. Our findings highlight the potential of Siparuna essential oils in mosquito management by impacting mosquito fitness beyond acute mortality.