As the deficiency worsens, the interveinal area becomes yellowish white, and the veins lose their green color. This is accompanied by defoliation and twig dieback. The deficiency is accentuated by excess soil moisture and low oxygen content in the soil. The use of less water, by shifting to the alternate middle procedure of irrigation or replacing furrows with sprinklers, is sometimes helpful. Chelate forms of iron have given variable results.
Annual applications appear necessary.
The avocado is particularly sensitive to salts. It accumulates chlorides and sodium more readily than most other tree crops. An accumulation of chloride manifests itself as a tip and marginal burn of the older leaves, premature defoliation, and sometimes a progressive mottled yellowing behind the burn. Excess sodium shows up as an interveinal leaf burn along with twig dieback. A rapid burn of the leaves at the tips or at the base of the leaf followed by defoliation suggests either an excessive fertilizer application or inadequate irrigation.