Chemical Compositions of Ligusticum chuanxiong Oil and Lemongrass Oil and Their Joint Action against Aphis citricola Van Der Goot (Hemiptera: Aphididae)

In order to develop novel botanical insecticides, the joint action ofLigusticum chuanxiongoil (LCO) and lemongrass oil (LO) againstAphis citricolavan der Goot was determined systematically indoors and outdoors. The chemical profiles of LCO and LO as determined by gas chromatography–mass spectrometry (GC-MS) analysis revealed that the main compounds from LCO were (Z)-ligustilide (44.58%) and senkyunolide A (26.92%), and that of LO were geranial (42.16%) and neral (32.58%), respectively. The mixture of LCO and LO showed significant synergy againstA. citricola, with a common-toxicity coefficient (CTC) value of 221.46 at the optimal ratio of LCO to LO (4:1,w:w). Based on the results of solvents and emulsifiers screening,L. chuanxiongoil·Lemongrass oil 20% emulsifiable concentrate (20% LCO·LO EC) was developed, and its stability was confirmed with tests of cold and thermal storage. Field trials indicated that the insecticidal activity of the diluted 20% LCO·LO EC (1000 fold dilution) was comparable to conventional pesticide (20% imidacloprid EC) onA. citricolaseven days after application. Thus, the mixture of LCO and LO has the potential to be further developed as a botanical pesticide.Keywords:lemongrass oil;Ligusticum chuanxiongoil;Aphis citricolavan der Goot;botanical aphicides