Nowadays, the use of nanoencapsulation technology of pesticides causes increase in efficiency and controlled release of these substances. In this study, the antifeedant and repellent activities of nanoencapsulated formulation (NEF) of wormwood sagebrush Artemisia sieberi Besser essential oil wereinvestigated against the elm leaf beetle Xanthogaleruca luteola (Muller). The experiments were conducted at 25 ± 2 °C, 65 ± 5% RH and a photoperiod of 16:8 h (L: D). NEF decreased the nutritional indices significantly compared to non-formulated oil.. NEF at a concentration of 4000 ppm, reduced efficacy of conversion of ingested food and efficacy of conversion of digested food in larvae, twice lower compared to pure essential oil. The repellency of non-formulated essential oil at a concentration of 8000 ppm reached it’s highest level after 6 h exposure, while the repellency of NEF increased over time and reached to 100% after 24 h and continued for 72 h. Therefore, further investigations are necessary to consider the NEF made by the A. sieberi essential oil as an effective toxicant against the elm leaf beetle.