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Shade tree decline
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Many trees around Dawson County are showing dieback and decline symptoms.

Twig or branch dieback is initiated in the tree as a response to poor growth conditions and/or pest attack. Usually a combination of physical, climatic, and pest problems lead to the tree shutting off some of its outside portions.

Tree decline is a general loss of vitality throughout the entire tree caused by a systemic disease or by a sequence of stressing events that cause the tree to burn too much food energy. Many cultural factors and past tree abuse predisposes a tree to decline.

Drought has been the main contributing factor to shade tree decline in recent years.

Extended drought can influence the health of shade trees by the loss of absorbing roots which are found primarily in the top 8-12 inches of soil.

Once this soil area dries, many absorbing roots dry out and die. Leaves and stems can also be damaged by drought conditions especially when the tree does not have water available for evaporative cooling and food production.

A season-long drought period with high temperatures can adversely affect all trees even if supplemental water is added.

Trees may not readily show initial symptoms because of stored carbohydrates and essential elements in the woody tissues.

As soon as these stored foods are near depletion, the trees begin to prematurely defoliate. Other drought symptoms can be delayed two or more years making it hard for many to believe that drought was actually the problem.

Mechanical injury is a major reason for shade tree decline.

In subdivisions and new housing developments, shade trees are often abused, roots are torn out of the ground, bark is bruised and soil around the trees is disturbed.

Losses from such damage could be minimized or even avoided if people realized that trees may not survive such treatment and took precautions to avoid abusing them. Root loss contributes to the weakening and decline of a tree's crown.

As with drought, these symptoms can be often delayed in appearance by 1-2 growing seasons.

Some of the worst things you can do to a tree is add soil fill around the trunk, cultivate or remove soil from around the trunk, compact the soil especially when the soil is wet or damage the bark on the stem.

Each of these events can lead to a weaker tree and can lead to other stress factors or pests injuring the tree further.

Remember insect and disease are especially likely to take advantage of a weak tree.

Now, what can be done to prevent shade tree decline?

The key to good health is tree vigor.

Provide a site that is suitable for the species involved. Pick a strong species of tree. Provide construction protection for roots and trunks of trees to reduce accidental injury, soil compaction and to allow adequate room for tree growth.

You should also plan ahead for future development.

When roots are damaged or lost, continue to water and wait one growing season and then thin the crown. This helps the remaining roots sustain the health of the existing foliage.

Shade tree decline is becoming more prominent.

Being able to recognize conditions which promote decline and taking steps to eliminate stresses before symptoms occur will save many shade trees.

Clark Beusse is the Dawson County extension agent. For more information, call (706)265-2442.