Huanglongbing (HLB) is a bacterial disease that is spread by an insect, the Asian citrus psyllid. This two-page fact sheet, which is best viewed as a PDF, http://edis.ifas.ufl.edu/pdffiles/PP/PP32800.pdf, explains how to tell the difference between HLB symptoms and symptoms from nutrient deficiencies. Written by T. Vashisth, M.M. Dewdney, and J.D. Burrow and published by the Plant Pathology Department.