Identification of Aggregation Pheromone as an Attractant for Odontothrips loti, A Serious Thrips Pest on Alfalfa

Odontothrips loti (Haliday) (Thysanoptera: Thripidae) is one of the most serious pests on alfalfa, causing direct damage by feeding and indirect damage by transmitting plant viruses. This damage causes significant loss in alfalfa production. Semiochemicals offer opportunities to develop new approaches to thrips management. In this study, behavioral responses of female and male adults of O. loti to headspace volatiles from live female and male conspecifics were tested in a Y-tube olfactometer. The results showed that both male and female adults of O. loti were attracted to the odors released by conspecific males but not those released by females. Headspace volatiles released by female and male adults were collected using headspace solid-phase microextraction (HS-SPME). The active compound in the volatiles was identified by gas chromatography-mass spectrometry (GC-MS). The analysis showed that there was one major compound, (R)-lavandulyl (R)-2-methylbutanoate. The attractive activity of the synthetic aggregation pheromone compound was tested under laboratory and field conditions. In an olfactometer, both male and female adults showed significant preference for synthetic (R)-lavandulyl (R)-2-methylbutanoate at certain doses. Lures with synthetic (R)-lavandulyl (R)-2-methylbutanoate significantly increased the trap catches of sticky white traps at doses of 40-80 µg in the field. This study confirmed the production of aggregation pheromone by O. loti male adults and identified its active compound as (R)-lavandulyl (R)-2-methylbutanoate, providing a basis for population monitoring and mass trapping of this pest.