Characterizing the vector competence of Diaphorina citri Kuwayama for ‘Candidatus Liberibacter asiaticus,’ the pathogen causing citrus greening, is essential for understanding the epidemiology of this disease that is threatening the U.S. citrus industry. Vector competence studies have been difficult because of the biology of D. citri, the inability to culture the pathogen, and the available diagnostic methods used to detect the bacteria in plant and insect tissues. The methods employed in many studies of D. citri vector competence may have overestimated amounts of live ‘Ca. L. asiaticus’ in both plant and insect tissues, and it is possible that the amounts of phloem ingested by psyllids may not contain sufficient detectable pathogen using current diagnostic methods. As a result of the difficulty in characterizing D. citri vector competence, the several daunting challenges for providing D. citri that are unable to inoculate ‘Ca. L. asiaticus’, as a novel method to control greening are discussed. Suggestions to overcome some of these challenges are provided.