Effect of photoperiod and gender on the feeding behavior of Asian citrus psyllid (Diaphorina citri Kuwayama)

Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae), transmits the Huanglongbing pathogen, Candidatus Liberibacter asiaticus. Because this bacterium is restricted to phloem and bacterial transmission is the result of psyllid feeding, D. citri is thought to be primarily a phloem-feeding insect. Yet, little investigation of the basic feeding behavior of D. citri has been done. In this study, an electrical penetration graph (EPG) monitor was used to: 1) examine the effects of photoperiod on D. citri feeding activities. and 2) determine whether gender-based differences in feeding behavior exist for D. citri. In the first experiment, examining the effects of photoperiod on D. citri feeding, within-treatment analysis showed that non-probing activities, phloem penetration and salivation, and xylem ingestion were generally longer in duration per insect during the light (photophase). In contrast, stylet pathway activities and phloem ingestion were longer in duration during the dark (scotophase). In the second experiment, investigating gender-based differences in D. citri feeding behavior, overall, the number of male D. citri reaching the phloem was 20% higher compared to females. However, the mean duration of phloem ingestion per insect was significantly higher for female D. citri compared to males. Analysis within treatments (gender) showed that, despite being considered a phloem feeder, the duration of xylem ingestion and phloem ingestion were not significantly different. Thus, results suggest that photoperiod and gender have an influence on D. citri feeding behavior, and are important variables for experiments investigating the transmission of Candidatus Liberibacter asiaticus by D. citri.