A comparative study of Eucalyptus salubris essential oils efficacy extracted by innovative and conventional processes against Sitophilus oryzae

The main objective of the present study is to introduce a new and ecologically safe method for managing the rice weevil, Sitophilus oryzae. Therefore, Eucalyptus salubris leaves essential oils yield, chemical composition and its insecticidal activity against the adults of S. oryzae were evaluated. Moreover, a comparison of innovative and conventional extraction methods of Eucalyptus salubris essential oils collected from two arboreta in south of Tunisia (Zrig and El-Hamma) was investigate. In fact, results demonstrated that essential oils yields varied depending on the arboreta and extraction methods. Essential oils yields obtained with MAE were increased in both arboreta. Besides, results showed a significant positive association between the essential oils yields of MAE and altitude of the arboretum. These results can be used to improve the production of oils in commercial plantations. Analysis of essential oils has shown that chemical composition may differ not only in the quantity of the different compounds but also in the quality of molecules extracted, depending on the method of extraction and harvest area. Moreover, E. salubris essential oils from El-Hamma were rich in hydrocarbon monoterpenes (56%), while those from Zrig were rich in oxygenated monoterpenes (39.6%), mainly 1, 8-Cineole (30.94%). Furthermore, the fumigant toxicity varied with the harvest area, extraction process, oil concentration and exposure duration. The conventional method achieved the best performances. The Lethal Concentration (LC50) values were 25.96 μL/L air, 34.43 μL/L air and 46.74 μL/L air for E. salubris essential oils collected from El-Hamma and extracted by hydrodistillation, ultrasonic-assisted extraction and microwave-assisted extraction, respectively. Overall, extraction of essential oils out by different techniques and innovative methods avoids shortcomings of content optional techniques friendly to environmental to avoid chemical risk, extraction time and obtain yield quality of essential oils.