Iron Deficiency Chlorosis

SYMPTOMS: This disorder causes the leaves of susceptible trees and shrubs to turn yellow (chlorotic) in the interveinal areas while the leaf tissue along the veins remains green. In severe cases, the leaves also turn brown along the edge, the leaves will be undersized, and branches or the entire tree may die.

CA USE: Chlorosis is the yellowing of leaves resulting from a lack of chlorophyll, the green pigment in leaves responsible for the production of a plant's food. The loss of the green chlorophyll reduces the efficiency of the leaf in manufacturing food and can lead to reduced vigor, stunting, and the eventual death of susceptible trees and shrubs.

Iron deficiency chlorosis occurs in alkaline soils with a pH above 7.0 which causes iron in the soil to become unavailable for root A red oak leaf showing the absorption. Iron is necessary for the formation of chlorophyll typical symptoms of iron and a deficiency causes the characteristic yellowing between leaf deficiency chlorosis. veins. Iron deficiency chlorosis commonly occurs in pin oak, white oak, red oak, willow oak, sweetgum, birch, magnolia, pine, holly, rhododendron, azalea, and other "acid-loving" plants.

Poor drainage, soil compaction, and construction damage, particularly of older trees, can ag- gravate the symptoms of this nutrient deficiency, or cause symptoms that mimic iron deficiency chlorosis.

SOLUTION: Soil incorporation of iron and/or acidifying compounds may be helpful for mildly chlorotic trees and shrubs. Soil treatments are often slow in producing results and require reapplication in subsequent years.

Trunk injections are capable of saving severely chlorotic trees that may otherwise die because of a lack of response to soil treatments. Injection of a liquid iron solution directly into the lower trunk will generally provide better leaf color the same season, although tree response may not be uniform because of irregular distribution. Foliage injury can happen occasionally and may appear as moderate leaf drop, leaf discoloration, or both. However, no permanent ill effects are likely to occur. Trees should not be injected annually.

Iron deficiency chlorosis treatments will not give permanent results and should be repeated periodically to maintain healthy trees and shrubs. Response to the chlorosis treatment is improved when the plant is fertilized at the same time.

Printed in U.S.A. T55-92-2W