Technical Abstract: Studies were conducted during 2005 and 2006 to assess population densities and phenology of the psyllid Diaphorina citri Kuwayama in citrus within east central Florida. Young, irrigated grapefruit and mature, non-irrigated orange trees were sampled weekly for eggs, nymphs and adults on flush shoots; for adults on mature leaves; and for adults captured on yellow sticky card traps. Since infestations of immature D. citri develop strictly on young flush, the abundance of flush was assessed weekly. Overall means of 26.5, 16.8 or 0.27 eggs, nymphs or adults per flush shoot, respectively, were observed in the young trees. In the mature trees, overall means of 16.0, 12.7 or 0.31 eggs, nymphs or adults per flush shoot were observed, respectively. Flush abundance was an inconsistent indicator of the mean density of D. citri per flush shoot. Mean density per shoot by itself was an inconsistent indicator of overall population levels of D. citri because few shoots were sometimes present when mean densities per shoot were high. An index of abundance based on both flush abundance and mean density of D. citri per flush shoot provided a more realistic measure of population levels. May, June and July were periods of time when immature D. citri were consistently present and most abundant, but the study indicated large infestations may occur at any time of the year depending on environmental factors and flush availability. Yellow sticky traps were effective for both male and female D. citri. The research indicated trap captures are useful for detecting adults and for gauging population trends of adults on mature leaves.