Chlorosis is a serious issue of shade trees where the plant is unable to properly manufacture chlorophyll.  Chlorophyll is an important leaf component which is responsible for energy absorption for the entire tree.  Trees without enough chlorophyll will not be able to grow and live.  If this condition is not corrected, the tree will eventually die.  The causes of chlorosis are complex and not entirely understood.  As a general rule, it is caused by the lack of a micro-nutrient or combination of micro-nutrients that a tree needs to manufacture chlorophyll.  

Iron and manganese are the common micro-nutrient deficiencies that cause chlorosis in shade trees.  These minerals are often not lacking in the soil, rather a condition exists where the tree’s root system is unable to obtain them in usable forms.

Since chlorophyll is what causes the tree to be green, chlorotic trees will often show symptoms where the color of the tree is light green, yellow, reddish and in severe cases white.  Manganese (Mn) and iron (Fe) are often difficult to distinguish from each other without foliar chemical analysis.  

Some researchers suggest the fine veins in the leaves will become chlorotic with Mn deficiency while they remain green on Fe deficient trees.  In practice, this is difficult to determine in the field so most Mn and Fe deficiencies are diagnosed by commonly affected species (maples more frequently have Mn deficiency, whereas birch and oak have Fe deficiency).  

Both Fe and Mn deficiencies often develop in the newer growth first.  Trees that are severely affected may exhibit tip dieback and decline and become more susceptible to other insect, fungal, and abiotic stresses.

Verdur is intended to be used as part of a broader management plan for treating chlorosis.   The practitioner must address the underlying factors that cause chlorosis in the overall management strategy.  While applications of Verdur may cause a green up for several years, consider other treatments like pH adjustment of soil, decompaction, and practices that stimulate root development.