Visual perception and color discrimination of the Asian citrus psyllid

The spectral sensitivity of adult Asian citrus psyllids, Diaphorina citri Kuwayama (Hemiptera: Liviidae), a vector of huanglongbing, was determined as a basis for optimization of visual traps. Electroretinogram responses were obtained from compound eyes of dark-adapted psyllids that were exposed to monochromatic 200 ms light flashes ranging from 340-700 nm. The spectral sensitivity curves were comprised of a peak in the ultraviolet region as well as a broad peak in the green-yellow region of the visual spectrum. Curves of male and female psyllids were similar and combined for further analysis. By fitting visual pigment templates to the curves, contributions from photopigments with maxima at 350, 430, 500, and 580 nm were revealed. In paired-choice attraction assays with sticky cards comparing colors at different intensities to grays of matching brightness, yellow and green were strongly attractive across the range of intensities, blue was generally repellent and red was not different than gray in attraction. By aligning specific photopigment sensitivities with behavioral preferences, this study establishes the physiological mechanisms underlying psyllid color attraction to guide the development of targeted visual monitoring tools.