Host-location behavior of the tea green leafhopper <italic>Empoasca vitis</italic> Göthe (Hemiptera: Cicadellidae): olfactory and visual effects on their orientation.

The tea green leafhopper, <italic>Empoasca vitis</italic> Göthe, is one of the most serious pests in tea growing areas. This study investigated the roles played by olfaction and vision in host orientation behavior. The compound eye of <italic>E. vitis</italic> was found to be a photopic eye; few olfactory sensilla were found on the antennae, while abundant gustatory sensilla were recorded on the mouthparts. Three opsin genes (<italic>EV_LWop</italic>, <italic>EV_UVop</italic>, <italic>EV_Bop</italic>) were isolated and found to be mainly expressed in the compound eye compared with other parts of the body. Immunolocalization indicated that the opsins mainly located in the different regions of rhabdom. The transcription levels of <italic>EV_LWop</italic>, <italic>EV_Bop</italic> and <italic>EV_UVop</italic> were reduced by 77.3, 70.0 and 40.0%, respectively, by RNA interference induced by being fed a special RNA-rich diet for 6 days. The rate of tropism to host color was effectively impaired by 67.6 and 29.5% in the ds<italic>EV_LWop</italic> and ds<italic>EV_Bop</italic> treatment groups, but there was no significant change in the ds<italic>EV_UVop</italic> group. The determination of the cause of the tropism indicated that odors from the host over long distances were unable to attract <italic>E. vitis</italic> and were only detected when the insects were close to the host. The developed compound eye of <italic>E. vitis</italic> plays a leading role in host location, and the long-wavelength opsin significantly affects the tropism to host color; the lack of olfactory sensilla results in long-distance odors not being able to be detected until the insect is near to the host-plant. The understanding of these behavioral mechanisms, especially the importance of opsin genes is expected to be useful for pest management. [ABSTRACT FROM AUTHOR]