Mobility within tree: Low

Uptake Form: Fe²⁺

Function: chlorophyll synthesis, metabolic process, enzyme activation

Deficiency/Toxicity Symptoms:  Iron deficiencies are often linked to over-watering, perched water tables, or calcareous soils (pH>7).  Iron deficiencies presence and severity may vary from year-to-year, depending on variations in rainfall and irrigation water management (Sallato et al. 2019). Poor soil physical conditions enhance the chance of Fe deficiencies. Since Fe is needed for chlorophyll synthesis, Fe deficiency is seen as chlorosis in the youngest leaves.  The interveinal tissue becomes pale green, yellow or white, but the veins stay green.  Iron toxicity is rare in the field.  It is often associated with a Mn deficiency.

Iron (Fe) Sources and Application

Foliage may be made greener by foliar application of iron chelate products.  This is a provisional measure and does not correct the basic cause, thus yearly application may need to be part of the orchard spray program if the underlying problem is a difficult to correct high soil pH condition.  Although a temporary measure, it still can make an improvement in stem quality of cherries where Fe deficiency is causing a problem. Soil and leaf tissue tests are not definitive and have not shown a good correlation with active Fe and nutrient deficiency (Sallato et al. 2019).

When Fe deficiency is severe, repeat foliar application once or twice at 10-day intervals.  It is best to apply early in the spring, under cooler temperature due to burning risk to plant tissue.   Iron sprays may not be combined with sprays of pesticides or other minerals.  Applied alone, they have occasionally injured sweet cherry and pear foliage and fruit.  Dilute application is not recommended. The recommended Fe foliar application rates are presented in Table 24. 

Table 1. Possible iron foliar application rates