Technical Abstract: The Asian citrus psyllid, Diaphorina citri, is a critically important citrus pest in the United States because it vectors the pathogen responsible for citrus greening disease (huanglongbing). The psyllid is attacked in Asia by the encyrtid parasitoid Diaphorencyrtus aligarhensis, and it would be desirable to establish this natural enemy in the United States for additional biological control of the psyllid. Despite releases of thousands of D. aligarhensis in 2000-2002 (Tawain population) and over 11,000 in 2007-2009 (mainland China population) in numerous counties throughout the citrus growing regions of Florida, D. aligarhenisis appears not to have established to date. Factors contributing to this apparent failure include intense pesticide use to control D. citri, low and variable populations of immature psyllids, competition with another parasitoid T. radiata (the two parasitoid species coexist in many parts of Asia), and predation of parasitized hosts by generalist predators. In light of these factors, further efforts to establish the parasitoid in Florida are warranted.