Abstract

Neely, Dan. 1974. Iron deficiency chlorosis of shade trees. Proc. Midwestern Chapter, I.S.T.C. 29: 2-8.

Iron deficiency chlorosis has been recognized in various parts of the world for over 100 years. It has been a problem of a wide variety of orchard, garden, and field crops in the western United States. The characteristic symptom of iron chlorosis in trees is a yellowing of the leaf blade in the areas most removed from the veins. As the deficiency becomes more severe, results of the shortage of chlorophyll and food production in the leaf become evident. Over a period of years, unless treatment is given, the trees die. The relationship between high soil pH and the unavailability of iron to plants is being extensively studied but is still not well understood. Susceptible plants growing in soils with a pH of 6.7 or above are frequently victims of iron chlorosis. Man learned over 100 years ago that adding iron to plants often corrects chlorosis. The iron source first and most often used in treatment of iron deficiency is iron sulfate. It is abundant, cheap, and readily available. Unfortunately, it is not the most effective iron source. The development of synthetic iron chelates in the 1950’s has improved chlorosis control recommendations greatly. Correction of chlorosis by foliar sprays has been usually only moderately successful. Iron chelates for use in soil treatments have been given much attention in recent years. The remaining control measures for correcting iron chlorosis involves the injection or the implantation of iron salts into the trunks of affected trees. Soil injections and trunk implantation treatments have consistently given prompt and thorough correction of iron chlorosis.

• © 1975, International Society of Arboriculture. All rights reserved.