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

Abstract

The tea green leafhopper, Empoasca vitis 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 E. vitis 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 (EV_LWop, EV_UVop, EV_Bop) 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 EV_LWop, EV_Bop and EV_UVop 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 dsEV_LWop and dsEV_Bop treatment groups, but there was no significant change in the dsEV_UVop group. The determination of the cause of the tropism indicated that odors from the host over long distances were unable to attract E. vitis and were only detected when the insects were close to the host. The developed compound eye of E. vitis 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.

The expression and function of opsin genes related to the phototactic behavior of Asian citrus psyllid

“…Opsin is the central factor that influences the phototactic behavior of many insects. In the tea green leafhopper, dsEV_LWop and dsEV_Bop exhibited a higher inhibitory effect on tropism behavior . Surprisingly, in honeybee knock‐down of the long‐wavelength receptor does not significantly change the physiological properties of the retina .…”

“…Apposition eyes exhibit the characteristics of high resolution and low optical sensitivity, which are helpful for diurnal insects . Many diurnal insects use the visual sense as the primary component of host‐plant location . Within the tree canopy, the olfactory and auditory senses are used to search for flush leaf and mates .…”

Susceptibility of Selected Tea Shoots to Oviposition by Empoasca onukii (Hemiptera: Cicadellidae) and Feasibility of Egg Removal with Harvesting

“…Little was known about the modalities of E. onukii oviposition behavior [18,19]. The results of this study indicated that most of the eggs were laid within the 3rd and 4th leaf order interval classes, whereas a low proportion of the eggs were detected within the leaf order interval classes below the 4th leaf order interval.…”

Foliage Intensity is an Important Cue of Habitat Location for Empoasca onukii

“…For example, chemical stimuli from the foliage of cotton could only be detected by Empoasca devastans from 1 cm, but visual stimuli were effective at up to 3.6 m (i.e., vision is the only option for E. devastans from a range from 1 cm to 3.6 m) [ 7 ]. Odors from the host were unable to attract E. vitis over long distances (>20 cm), across which visual cues (color) are the dominant information for E. vitis in selecting habitat [ 8 ]. Visual cues may play an important role in habitant location at a distance for E. vitis adults.…”