Contact Toxicity and Repellency of the Essential Oil from Bupleurum bicaule Helm against Two Stored Product Insects

Abstract

Essential oils obtained from many plants showed various kinds of insecticidal properties; some of them have been considered as alternative insecticides for pest control. The present study was aimed at determining the chemical composition of the essential oil from the roots of Bupleurum bicaule Helm, as well as evaluating the contact and repellent activities of the oil and four identified compounds against Lasioderma serricorne and Liposcelis bostrychophila adults. The essential oil was extracted by hydrodistillation, and its components were analyzed by gas chromatography-mass spectrometry (GC-MS). 26 components were determined and the main compounds included trans-2-isopropylbicyclo[4.3.0]non-3-en-8-one (25.9%), 4,5-dimethyl-1,2,3,6,7,8,8a,8b-octahydrobiphenylene (23.5%), and 1,4-dimethoxy-2-tert-butylbenzene (4.3%). It was found that the essential oil exhibited contact toxicity against L. serricorne (LD50 = 11.91 μg/adult), but the contact toxicity against L. bostrychophila could not be observed. The essential oil also showed strong repellent activity against L. serricorne with percent repellency of 100% at 78.63 nl/cm2. Four chemical compounds, 1,4-dimethoxy-2-tert-butylbenzene, bornyl acetate, (2E,4E)-2,4-nonadienal, and β-bisabolene, exhibited various levels of bioactivities. The experimental results indicated that the essential oil of B. bicaule and its individual compounds could be used in insecticidal and repellent strategies for stored product insects.