As the vector of the global disease of citrus greening or huanglongbing, Asian citrus pysllids, Diaphorina citri Kuwayama (Hemiptera: Liviidae), are the greatest threat to the worldwide citrus industry. Critical to management of D. citri and huanglongbing is optimization of surveillance methodologies. Although phytophagous insects may find host plants by multimodal cues, some appear to primarily use visual cues. In this study, we examined the behavior of Asian citrus psyllids toward light from light-emitting diodes (LEDs) in the insect visible spectrum. The periodicity of attraction of psyllids to visual cues was evaluated in the field (yellow sticky traps) and laboratory (multi-colored LEDs) with a strong peak of activity during the afternoon in both the field and the laboratory (both 14:00 to 18:00 hours). In laboratory evaluations of psyllids to differently colored LEDs, strongest attraction was to LEDs emitting ultraviolet (390 nm), green (525 nm), and yellow (590 nm) light. Male and female psyllids did not differ significantly in their responses to visual cues. These findings provide the basis for formulating better traps that reflect UV and yellow light and potentially incorporate UV LEDs for monitoring psyllids and a better understanding of Asian citrus psyllid visual behavior.

The Asian citrus psyllid, Diaphorina citri, vectors huanglongbing (HLB), the most serious disease affecting citrus globally. D. citri and HLB have spread to the major citrus growing regions of North America causing billions of dollars of damage in Florida alone. The visual behavior of D. citri is not well characterized and more knowledge is needed to improve attractive traps for monitoring and control of the D. citri. Bioassays were conducted to evaluate attraction to light transmitted through different colored filters. The addition of ultra-violet light (< 400 nm) enhanced attraction of D. citri to transparent visual targets made of green or yellow filters. However, attraction to blue targets was unaffected by UV light. This is the first study to demonstrate a phytophagous insect responding to a hue that is a combination of long and short wavelengths. Further testing is needed to determine how D. citri uses such discriminatory powers in the field. Our results further imply that D. citri utilize color vision, as the less intense yellow and green hues were chosen over white light. In summary, this research provides an increased understanding of D. citri visual behavior and can be used for the development of a more attractive D. citri trap than those currently available.

Mate-seeking in Diaphorina citri Kuwayama, a vector of the economically damaging huanglongbing citrus disease, typically includes male—female duetting behaviors. First, the male calls by beating his wings at ≈170–250 Hz, producing vibrations that are transmitted along the host tree branches to the female. If receptive, she immediately replies, helping to direct the searching male toward her. The duetting and searching continues until the male locates the female. Males and females are similar in size and produce wingbeat vibrations with similar temporal and spectral patterns. A study of male and female responses to playbacks of recorded and synthetic mimics of different vibrational signals on citrus plants was conducted to better understand the range of signals to which D. citri respond and potentially to co-opt or disrupt their vibrational communication. In general, both sexes responded well to a variety of 0.3–0.5-s signals that included multiple harmonics of ≈200-Hz wingbeatfrequency chirps up to ≈1,400 Hz (where a chirp is a sine wave tone that sweeps across a narrow range of frequencies). There were only minor differences in female responses to signals containing different relative amplitudes of such chirps, and males readily located sources that played these multipleharmonic signals. The results are discussed in relation to mating-signal selectivity and the potential for developing automated methods to trap male D. citri by using vibrational signals.