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