Source or Sink? The Role of Residential Host Plants in Asian Citrus Psyllid Infestation of Commercial Citrus Groves.

Citriculture landscapes in the U.S. are typically habitat mosaics of commercial groves interspersed with residential areas supporting a variety of unmanaged citrus. Diaphorina citri the vector of Candidatus Liberibacter asiaticus, the causal agent of Huanglongbing feeds on citrus in both habitats. We postulated that residential citrus function as a 'source' of D. citri that infest groves, functioning as sinks. Here we report on an experimental mark-release-recapture study conducted at the interface of a residential neighborhood and groves. Adult D. citri marked with colored fluorescent powders were released in both habitats (n = 15,300) and their movement within and between milieus monitored. Although the recapture rate of marked psyllids was very low (0.23%), the results were instructive. Most of the recaptured psyllids in residential trees (84.6%) were released within that habitat. In contrast, approximately half of the marked psyllids recovered in groves were released in residential areas. Of all the recaptured psyllids, about 40% changed habitats, but the change was skewed toward movement from residential to grove habitat. These data strongly suggest that there is a constant exchange of D. citri adults between the two habitats, with residential citrus trees functioning as a source habitat of psyllids. The further the residential trees are located from groves, the less likely they will serve as sources of D. citri. Hence, to reduce the risks of citrus grove colonization by D. citri, new groves should be established away from residential habitats where possible, and psyllid management practices must also be implemented in residential habitats.