Insecticidal activity of essential oil from Cephalotaxus sinensis and its main components against various agricultural pests

Plant essential oils (EOs) could be used as new alternatives of synthetic insecticides due to their environmental friendliness, safety to non-target organisms, and low-level resistance. In this study, the essential oil of Cephalotaxus sinensis (CSEO), an important Chinese medicinal species, showed potent insecticidal activity against Megoura japonica, Plutella xylostella and Sitophilus zeamais in laboratory bioassays; CSEO 20 % emulsifiable concentrate exhibited the control efficacy of 85.67 % against M. japonica after 7 days treatment at concentration of 0.25 % (w/v) in the greenhouse experiment. The GC-MS results showed that the main components of CSEO were alpha-pinene (37.89 %), beta-caryophyllene (16.78 %) and germacrene D (10.79 %). Five active compounds, beta-elemene (1), beta-caryophyllene (2), beta-phellandrene (3) caryophyllene oxide (4) and alpha-pinene (5) were isolated from CSEO. beta-Caryophyllene (2) exhibited highest contact toxicity against M. japonica and P. xylostella, with the median lethal dose (LD50) values of 0.072 mu g/adult and 0.32 mu g/larva, respectively. alpha-Pinene (5) showed the highest fumigant toxicity against M. japonica and P. xylostella, with the median lethal concentration (LC50) values of 6.74 and 7.35 mg/L, respectively. Furthermore, beta-phellandrene (3) had the potent contact and fumigant toxicity against S. zeamais with the LD50 and LC50 value of 2.19 mu g/adult and 3.57 mg/L, respectively. Thus, CSEO and their major components have the potential to be developed as novel botanical insecticides for the control of agricultural pests.