Identification of Terpenoid Compounds and Toxicity Assays of Essential Oil Microcapsules from Artemisia stechmanniana

SIMPLE SUMMARY: Plant essential oils, as biological pesticides, play a key role in chemical ecology. In this study, we analyzed the components of A. stechmanniana essential oil and identified 17 terpenoid compounds. A. stechmanniana essential oil showed a high efficiency compared with azadirachtin against Aphis gossypii, Frankliniella occidentalis, and Bactericera gobica of the wolfberry (Lycium barbarum L.) in indoor toxicity assays. For practical use, the A. stechmanniana essential oil microencapsule showed long-lasting insecticidal activity in the Lycium barbarum field. This study contributes to the identification of a new biopesticide from untapped Artemisia plants and the design of a novel method against pests of L. barbarum. ABSTRACT: Plant 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 of A. stechmanniana using gas chromatography–mass spectrometry (GC-MS). The results showed seventeen terpenoid compounds in the A. stechmanniana oil, 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 of Artemisia stechmanniana essential oil against Aphis gossypii, Frankliniella occidentalis, and Bactericera gobica in Lycium barbarum. The LC(50)/LD(50) values of A. stechmanniana essential oils against A. gossypii, F. occidentalis, and B. gobica were 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. stechmanniana essential 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 the A. stechmanniana microencapsule (AM) and doses at three concentrations was conducted in Lycium 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 untapped Artemisia plants and designed a novel method against pests using a new biopesticide on L. barbarum.