Leaf yellowing in about one-quarter of an orange tree canopy due to citrus greening or Huanglongbing, caused by a phloem-inhabiting bacterium spread by the Asian citrus psyllid, Diaphorina citri.

Leaf yellowing in about one-quarter of an orange tree canopy due to citrus greening or Huanglongbing, caused by a phloem-inhabiting bacterium spread by the Asian citrus psyllid.  Credit: Michael E. Rogers
Credit: Michael E. Rogers