Essential oil nanoemulsions enhance protection of stored tobacco against Lasioderma serricorne.

Essential oils present a promising botanical insecticide for sustainable pest control. Sourced from plants such as cinnamon, clove, and peppermint, these biocompounds are eco-friendly alternatives to conventional pesticides, employing unique modes of action. Their application is of relevance to the global tobacco industry, which suffers significant annual losses from insects during storage and handling. While several control strategies exist, heavy dependence on synthetic insecticides has resulted in pest resistance, environmental contamination, and harm to non-target organisms. This study explores how nanoemulsification can enhance the insecticidal efficacy of these essential oils. Using a high-energy ultrasonication method (20 kHz, 60% amplitude, 120 W, below 30 °C via ice-water bath, successfully, monodisperse nanoemulsions fabricated stable (NEs, surfactants Tween 80: Span 20 at 4:1 ratio). Transmission electron microscopy and dynamic light scattering revealed spherical particles with diameters between 15.77 and 46.27 nm (TEM) and 18.3–51.7 nm (DLS, PDI < 0.20). The formulations demonstrated kinetic, long-term, thermal, and centrifugal stability, possessed acidic pH values (4.50–5.60), and exhibited satisfactory physicochemical properties, including a zeta potential ranging from − 30.5 to − 50.5 mV. Bioassays for contact and fumigant toxicity showed that nanoemulsification significantly increased insecticidal potency against both adult and larval stages, with median lethal concentration (LC₅₀) values for the NEs 9.4 to 162.1 times lower than those of their pure essential oil counterparts. Clove NE was the most potent formulation overall, especially against larvae (LC₅₀ = 32.71 ppm). The NEs also produced steeper probit slopes than the pure oils, indicating a faster and more uniform toxic response. Mechanistic differences between life stages are discussed in the context of cuticle thickness and metabolic susceptibility. In simulated storage trials on treated tobacco leaves, NEs applied at a 25-fold lower concentration (40 ppm) achieved 70–90% mortality after 72 h, comparable to pure oils applied at 1000 ppm. Statistical analysis confirmed that concentration and exposure time were the primary factors influencing mortality, with a smaller but significant effect from the type of essential oil and no significant interaction effects. Fumigant toxicity bioassays further confirmed the superior efficacy of the NEs, with enhancement factors ranging from 17.1 to 143.5-fold over pure oils, as measured by reduced LC₅₀ values, and statistical significance was confirmed by non-overlapping 95% confidence intervals. Adults were consistently more susceptible than larvae across cinnamon and peppermint nanoemulsion treatments. The findings strongly support the use of clove, cinnamon, and peppermint nanoemulsions as highly effective, eco-friendly botanicals for protecting stored tobacco. Stability conclusions are limited to laboratory physicochemical indices, and future work should address real-world conditions and non-target effects.