Insecticidal efficiency of orange peel (Citrus sinensis) essential oil nanoemulsions against Rhyzopertha dominica (Fabricius, 1792) and Tribolium castaneum (Herbst, 1797)

The insecticidal efficiency of orange (Citrus sinensis) peel essential oil (OP-EO) is limited because of its low stability under environmental conditions. Nanoemulsion formulations show promise in overcoming this limitation. Therefore, this study aimed to formulate and characterize the OP-EO nanoemulsion form (OP-EON) and investigate its insecticidal properties against two significant storage pests, Rhyzopertha dominica (Fabricius, 1792), and Tribolium castaneum (Herbst, 1797). The OP-EON (4:3:3:90 w/w, EO: Tween 80: Ethanol: water) was successfully created using an ultrasonic homogenizer. The major chemical components of the OP-EO were determined to be D-limonene (87.93%), myrcene (3.62%), and α-pinene (1.34%) through GC-MS analysis. The OP-EON was characterized using TEM (50-100 nm), Zeta sizer (the mean droplet particle size of 58.60 nm, the ζ-potential value of -12.6 mV, and the polydispersity index of 0.486), and FT-IR analysis. After 7 days, exposure to 500 ppm of the OP-EON resulted in 50% and 30% mortality rates in R. dominica and T. castaneum, respectively. Exposure to 1000 ppm of OP-EON resulted in 90% and 55% mortality in R. dominica and T. castaneum, respectively, after 7 days. Overall, these results clearly showed the potential to exceed the limits of the insecticidal activity of the OP-EO with its nanoemulsion form.