Citrus: Iron Deficiency

Problem
Some of the leaves turn pale green or yellow. The newest leaves (those at the tips of the branches) are most severely affected. Except in extreme cases, the veins of affected leaves remain green. In extreme cases, the newest leaves are small and all white or yellow. Older leaves may remain green.

Analysis
Citrus trees frequently suffer from deficiencies of iron and other minor nutrients such as manganese and zinc, elements essential to normal plant growth and development. Deficiencies can occur when 1 or more of these elements are depleted in the soil. Often these minor nutrients are present in the soil but alkaline (pH 7.5 and higher) or wet soil conditions cause them to form compounds that cannot be used by the tree. An alkaline condition can result from overliming, or from lime leached from cement or brick. Regions where soil is derived from limestone, and those with low rainfall, usually have alkaline soil. Some citrus trees turn yellow naturally in cold weather. However, if iron is available, the foliage will turn green again when the weather warms.

Solution
Apply a chelated iron fertilizer to the foliage at 2-week intervals during the new- or rapid-growth period. Repeat treatment whenever new growth appears (do not apply if the temperature is expected to exceed 90°F within 24 hours of application). Or apply a fertilizer containing iron to the soil around the plants to correct the iron deficiency. Improve soil drainage (see Soil Types, Soil Structure, and Groundwater).