Most Susceptible Trees: Pin oak, silver maple, baldcypress, crabapple and sweet gum. Can also affect white pine, elm, London planetree, cottonwood, walnut, sugar maple, Eastern redcedar, Bradford pear and willow.

Description: Affected leaves turn a yellowish color while the leaf veins remain a dark green. Iron chlorosis is caused by the plant not being able to obtain the iron it needs. Iron is needed for the production of chlorophyll. Therefore, a lack of iron results in a loss of the green color in the leaves. In severe cases, leaf color may change from yellow to white to brown. If uncorrected, twigs and eventually branches may die leading to the death of the tree.

Symptoms may appear over the entire tree, on one side only, or be limited to individual branches.

Soils in Kansas usually have adequate amounts of mineral iron. However, as soil pH rises above 7.0, iron changes to an insoluble form that many plants have difficulty picking up.

Other Causes of Chlorosis: Iron deficiency is not the only cause of leaf yellowing. Herbicide damage or other mineral deficiencies such as nitrogen, manganese, boron or zinc may also result in chlorosis symptoms. Signs of manganese deficiency, in particular, may be similar to those of iron deficiency. The two can be distinguished by the broad bands of normal green color that remain next to the major veins if manganese is lacking. Leaves on the ends of the branches of manganese-deficient trees generally are not affected until late in the summer after growth has stopped.

In most cases, a foliar application of the deficient mineral early in the summer will cause a temporary green-up of the leaves. If application of the mineral thought to be deficient does not cause a temporary correction of the chlorosis, some other mineral deficiency is causing the problem. Other possible causes should be investigated.