Visual learning may influence host selection in Asian citrus psyllid, Diaphorina citri (Hemiptera: Liviidae)

The Asian citrus psyllid, Diaphorina citri, is an oligophagous herbivore that transmits Candidatus Liberibacter asiaticus, the devastating pathogen causing citrus greening disease.  Efforts to manage D. citri populations and slow the spread of the pathogen may be aided by an increased understanding of the mechanisms underlying D. citri host plant selection and acceptance.  Although specialists are largely regarded to rely on innate preferences for host selection, little research has been done to investigate the extent of learning in such organisms.  Previous work has indicated that D. citri are capable of simple olfactory associations.  However, it is currently unknown to what extent learned visual associations or the combination of olfactory and visual stimuli interact with innate responses to drive host selection. This study investigated the plasticity of a locomotor response after experience with single visual and olfactory stimuli, as well as to a compound stimulus.  Experienced D. citri were exposed to the novel test stimulus for three days while feeding on Citrus x aurantium. Naive D. citri encountered the test stimuli only during testing.  Behavior was measured in a choice test using a modified y-tube olfactometer.  Both male and female D. citri were found to have modified behavior after experience with single olfactory and visual stimuli.  However, only females were capable of discriminating between a visual and olfactory stimulus when presented as a compound stimulus.  Additionally, analysis of the latency to selection showed that experienced D. citri made decisions more quickly than naive D. citri.  The results of this study suggest that D. citri do acquire visual and olfactory information associated with the host plant environment and that experience with such stimuli can influence innate preference. Future research will investigate the extent to which such experience-mediated behavior influences host selection in the field.  If consistent with laboratory experiments, such data could provide a basis for predicting regional D. citri movement to enhance population monitoring and potentially reduce the use of pesticides in low-risk groves.