Nutrient deficiencies have a wide range of symptoms that will not be fully covered in this key. Things to look for are how symptoms are distributed throughout the tree and throughout the grove. Nutrient deficiencies tend to be more uniformly distributed in the tree than the diseases they are commonly confused with. A nutrient deficiency may express itself on the whole tree level causing twig die-back, long thin branches, yellowing, and reduced or abnormal growth. Nutrient deficiencies may alter fruit characteristics such as shape, hardness, peel thickness, and peel texture. Nutrient deficiencies may manifest on leaves resulting in chlorosis, enlarged or shrunken leaves, raised veins, unusual leaf patterns and changes in leaf coloration. For example, zinc deficiency will appear on new foliage throughout the tree in contrast to early HLB symptoms which are restricted to a single or a few shoots.
Serrano, D., Serrano, E., Dewdney, M., and Southwick, C. (2010). Citrus Diseases. USDA/APHIS/PPQ Center for Plant Health Science and Technology. [09-14]