Repellent activities of essential oils rich in sesquiterpenoids from Saussurea amara (L.) DC. and Sigesbeckia pubescens Makino against two stored-product insects.

The essential oils (EOs) from aerial parts of Saussurea amara (L.) DC. (SAEO) and Sigesbeckia pubescens Makino (SPEO) were analyzed for their chemical composition by GC-MS, and their repellent activities against adults of the red flour beetle, Tribolium castaneum Herbst, as well as the booklouse, Liposcelis bostrychophila Badonnel, were evaluated for the first time. Results of GC-MS analysis indicated that both SAEO and SPEO were characterized by high content of sesquiterpenoids (relative content > 70%) including oxygenated sesquiterpenoids. The two oil samples and their major component caryophyllene oxide exerted beneficial repellent effects on T. castaneum and L. bostrychophila at 2 and 4 h post-exposure. At 4 h post-exposure, the PR value of caryophyllene oxide could still reach 92% (class V) against T. castaneum at minimum testing concentration of 3.15 nL/cm, and this compound was observed to result in the greatest repellency (PR = 100%) against L. bostrychophila at 12.63 nL/cm. This work confirmed the potent repellent efficacy of SAEO and SPEO for controlling pest damage and suggested their potential to be developed into botanical repellents.