SYMPTOMS AND EFFECTS

Chlorosis is a common problem of some tree species in Michigan. Red Maples are especially susceptible, but occasionally Birch trees also show this condition. For some trees this condition is temporary and may not persist from year to year. However, for others this interveinal chlorotic condition may stay with the plant for years, slowly decreasing the overall vigor and ability of the tree to survive. The first indication of chlorosis is general yellowing or pale green coloring of the foliage.  As the condition worsens the leaves lose their ability to manufacture food and will die. As the tree loses stored energy, whole branches and portions of the tree may begin to die off. Over time the tree may decline enough to lose its aesthetic value, necessitating removal. 

CAUSE

Chlorosis is a disruption of chlorophyll formation in leaves. This disruption may be caused by a deficiency of elements like iron, manganese, zinc or copper. As the soil pH levels increase, nitrogen, potassium and phosphorus concentration increases in the foliage, causing a disruption of chlorophyll formation. Simply prescribing tree fertilization for chlorotic trees without analysis of current element levels in the foliage or soil could result in excesses that compound the situation.  Chlorosis sometimes involves a combination of factors including nutrient in-balance, soil pH level, poor site conditions, or system failure due to damaged roots.

CONTROL

Prevention is the best control. Do not plant trees susceptible to chlorosis in soils having a pH higher than 7.0 or in soils with low organic matter.  Be careful not to damage the roots during construction. If the problem is related to high soil pH, restoration of leaf color may be accomplished and maintained by soil acidification. The goal is to lower the soil pH below 6.5 and maintain that level in the future. Trunk injections supply manganese directly to the leaves. A single treatment may last more than one year, but when the condition returns the treatment will need to be repeated.