Electrophysiological and Behavioral Responses of Thrips hawaiiensis (Thysanoptera: Thripidae) to the Floral Volatiles of the Horticultural Plant Magnolia grandiflora (Magnoliales: Magnoliaceae).

Volatile cues are important in the host detection and discrimination of phytophagous insects, allowing them to find suitable hosts. Here, the electroantennography (EAG) and behavioral responses of female Thrips hawaiiensis to the floral volatiles of different plants, Magnolia grandiflora L. (Magnoliales: Magnoliaceae), Gerbera jamesonii Bolus (Asterales: Asteraceae), Lilium brownii Baker (Liliales: Liliaceae), and Rosa rugosa Thunb. (Rosales: Rosaceae), were studied. Y-tube olfactometer bioassays revealed that M. grandiflora was the preferred host for T. hawaiiensis. Fifty-two compounds were identified from the volatile profile of M. grandiflora by gas chromatography-mass spectrometry analysis, of which β-elemen (15.39%), bicyclogermacren (11.99%), and (E)-α-bisabolene (6.05%) showed the highest relative contents. The EAG bioassays revealed that the antennae of T. hawaiiensis could perceive these tested volatile compounds at different concentrations. In six-arm olfactometer bioassays, T. hawaiiensis showed significant positive responses to β-elemen and (E)-α-bisabolene at various concentrations, and 10 μg/μL was found to be the most attractive concentration for β-elemen, and 50 and 100 μg/μL for (E)-α-bisabolene. Based on the four-arm olfactometer bioassays, β-elemen was more attractive than (E)-α-bisabolene to T. hawaiiensis when compared at their optimal concentrations. Therefore, T. hawaiiensis could perceive and distinguish the floral volatiles from the preferred host plant (M. grandiflora). These findings assist in better understanding the mechanism of host preferences of T. hawaiiensis from a chemoecological perspective. In particular, β-elemen showed the greatest potential to be developed as a novel attractant for the monitoring and control of T. hawaiiensis.