How does infection of Diaphorina citri (Hemiptera: Psyllidae) with Candidatus Liberibacter asiaticus affect the behavioral response of the vector to healthy versus diseased citrus trees?

The Asian citrus psyllid, Diaphorina citri Kuwayama, is the most important pest of citrus worldwide because of its ability to vector Candidatus Liberibacter (Ca. Las) species, the presumed causal agents of huanglongbing (HLB). Pathogen-infected trees may exhibit altered volatile production and thus be differentially attractive to the D. citri vector as compared with healthy trees. We conducted a series of behavioral experiments to investigate whether HLB-infected citrus plants were differentially attractive to D. citri as compared with healthy citrus plants. We also examined if psyllids known to be infected with the pathogen behaved differently from uninfected controls in response to both healthy and HLB-infected plants. HLB-infected citrus plants were more attractive to D. citri adults than healthy plants in two-choice olfactometer experiments. In open-air cage experiments, more D. citri were attracted to HLB-infected plants than to healthy plants. However, subsequent dispersal of D. citri adults to healthly plants following their initial choice indicated that final setting preference was for healthy rather than diseased plants. These behavioral results were the same for psyllids that were unexposed to the pathogen and those that were confirmed carriers. Differences in volatile production between uninfected and HLB-infected plants will also be discussed.