Chemical composition and toxicity of essential oils to the green-aphid Schizaphis graminum (Rondani, 1852)

The aim of this study was to assess the chemical composition of essential oils of Illicum verum, Ageratum conyzoides,Piper hispidinervumand Ocotea odorífera, as well as their toxicity to the green-aphid Schizaphis graminum. Compound identification was carried out with gas chromatography + mass spectrometry, and quantification with gas chromatography + flame ionization detector, both with DB5 column. The hydrodistillation process promoted oil yield of 3.81% for I. verum; 0.46% for A. conyzoides; 2.85 % for P. hispidinervum;and 0.68 % for O. odorífera. The major components from the oils of A. conyzoides was precocene (87.0%) and (E)-caryophyllene (7.1%); (E)-anethol (90.4%), limonene (2.6%) and methyl-chavicol (1.3%) for I. verum; methyleugenol (81.2%) and safrole (10.6%) for O. odorifera; and safrole (82.5%) and α-terpinolene (13.4%) for P. hispidinervum. The acute toxicity test (24 hours) performed by contact in sorghum leaves or contaminated filter-paper showed that the higher toxicity occur with essential oils of A. conyzoides, with LC50of 7.01 and 7.01 µg oil/cm2, respectively; followed by O. odorifera, with LC50 of 17.10 and 66.70 µg oil/cm2, respectively; I. verum, with LC50of 66.40 and 65.40 µg oil/cm2, respectively; and low toxicity was observed for the P. hispidinervum essential oil, with LC50 of 64.00 and 143.00 oil/cm2, respectively. With the results obtained in this research, we can state that the use of these essential oils can be a new tool in integrated pest management.

本研究旨在评估真八角（Illicum verum）、胜红蓟（Ageratum conyzoides）、长柄胡椒（Piper hispidinervum）及芳香奥寇梯木（Ocotea odorífera）精油的化学成分，及其对麦二叉蚜（Schizaphis graminum）的毒杀活性。化合物鉴定采用气相色谱-质谱联用（GC-MS）技术，定量分析采用气相色谱-火焰离子化检测器（GC-FID），两种检测方法均使用DB5色谱柱。水蒸馏法提取的精油得率分别为：真八角3.81%、胜红蓟0.46%、长柄胡椒2.85%、芳香奥寇梯木0.68%。各精油的主要成分如下：胜红蓟精油为早落素（precocene，87.0%）与（E）-石竹烯（7.1%）；真八角精油为（E）-茴香脑（90.4%）、柠檬烯（2.6%）与甲基胡椒酚（1.3%）；芳香奥寇梯木精油为甲基丁香酚（81.2%）与黄樟素（10.6%）；长柄胡椒精油为黄樟素（82.5%）与α-松油烯（13.4%）。采用高粱叶片接触法与污染滤纸接触法开展24小时急性毒性试验，结果显示毒杀活性最高的为胜红蓟精油，其半数致死浓度（LC50）分别为7.01与7.01 µg油/cm²；其次为芳香奥寇梯木精油，LC50分别为17.10与66.70 µg油/cm²；真八角精油的LC50分别为66.40与65.40 µg油/cm²；长柄胡椒精油毒性最低，其LC50分别为64.00与143.00 µg油/cm²。基于本研究结果，上述精油可作为害虫综合治理的新型实用工具。