A tree that just doesn't look quite as healthy as usual, but does not have any specific disease or insect problem may be suffering from shade tree decline. Decline is a general term describing dieback of the branches in the crown, associated with a general reduction of tree vitality.

The symptoms usually develop slowly, and may not be noticed immediately. The leaves may become smaller and fewer in number. The crown of the tree often thins out. New terminal growth may be limited, and branches may die. Abnormally large seed crops are sometimes associated with decline, as is early fall color and leaf drop. Trees affected by decline may survive for many years, or may die within a few years.

Trees may decline for many reasons, often a combination of factors may be involved. Following is a list of factors that may contribute to tree decline:

• Long term leaf loss.
• Repeated leaf loss, from insects or diseases.
• Adverse weather conditions, such as rapid changes in winter temperatures, late spring and early fall frosts, and drought.
• Flooding, or changes in the water table.
• Bark damage from lawn mower injury, weed eaters, frost cracks, or animal feeding.
• Soil pH problems - usually when the soil is too alkaline.
• Injury from lawn weed killers or other chemicals.
• Damage from construction around the tree, such as soil fill, severe root loss, or soil compaction from heavy equipment.
• Accumulated salt injury from road salt.
• Restricted root development.
• Stem Girdling Roots
• Graft union failure.
• Root and trunk rot, as evidenced by mushrooms or other fungal structures.

Diagnosing shade tree decline is difficult and it is often impossible to confirm an exact cause. When diagnosing shade tree decline, remember that symptoms don't always occur immediately following the initial injury. Evaluate possible causes of plant stress over the past 5 years!

The best way to control tree decline, is to take preventative measures, and whenever possible, to avoid stress factors that contribute to the problem. If decline symptoms appear that can't be traced to a specific insect or disease, try to increase the health of the tree by mulching and providing additional water during dry periods. Prune out any dead wood or branches.

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