Simple SummaryPlant essential oils, as biological pesticides, play a key role in chemical ecology. In this study, we analyzed the components ofA. stechmannianaessential oil and identified 17 terpenoid compounds.A. stechmannianaessential oil showed a high efficiency compared with azadirachtin againstAphis gossypii,Frankliniella occidentalis, andBactericera gobicaof the wolfberry (Lycium barbarumL.) in indoor toxicity assays. For practical use, theA. stechmannianaessential oil microencapsule showed long-lasting insecticidal activity in theLycium barbarumfield. This study contributes to the identification of a new biopesticide from untappedArtemisiaplants and the design of a novel method against pests ofL. barbarum.AbstractPlant essential oils, as biological pesticides, have been reviewed from several perspectives and play a key role in chemical ecology. However, plant essential oils show rapid degradation and vulnerability during actual usage. In this study, we conducted a detailed analysis of the compounds present in the essential oils ofA. stechmannianausing gas chromatography–mass spectrometry (GC-MS). The results showed seventeen terpenoid compounds in theA. stechmannianaoil, with four major terpenoid compounds, i.e., eucalyptol (15.84%), (+)-2-Bornanone (16.92%), 1-(1,2,3-Trimethyl-cyclopent-2-enyl)-ethanone (25.63%), and (-)-Spathulenol (16.38%), in addition to an amount of the other terpenoid compounds (25.26%). Indoor toxicity assays were used to evaluate the insecticidal activity ofArtemisia stechmannianaessential oil againstAphis gossypii,Frankliniella occidentalis, andBactericera gobicainLycium barbarum. The LC50/LD50values ofA. stechmannianaessential oils againstA. gossypii,F. occidentalis, andB. gobicawere 5.39 mg/mL, 0.34 mg/L, and 1.40 μg/insect, respectively, all of which were highly efficient compared with azadirachtin essential oil. Interestingly,A. stechmannianaessential oil embedded in β-cyclodextrin (microencapsule) remained for only 21 days, whereas pure essential oils remained for only 5 days. A field efficacy assay with theA. stechmannianamicroencapsule (AM) and doses at three concentrations was conducted inLycium barbarum, revealing that the insecticidal activities of AM showed high efficiency, maintained a significant control efficacy at all concentrations tested, and remained for 21 days. Our study identified terpenoid compounds from untappedArtemisiaplants and designed a novel method against pests using a new biopesticide onL. barbarum.