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John Fulton

John Fulton
Former County Extension Director

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In The Backyard

Horticulture columns and tips done on a timely basis

Tree Decline

Posted by John Fulton -

When the entire tree looks like it is dieing, the injury, disease, or insect logically must be affecting the trunk or the roots. These areas would cut off the water supply to the entire tree. Look at the entire tree and compare it to nearby trees. Also consider when the problem started and what changed on the site about that same time. Healthy trees don't suddenly die because they are old. Many below ground reasons may cause tree decline. Drought, flooding, compaction of the root zone, poor soils, planting too deeply, inadequate space for roots and many other things could be involved. Often, diagnosing such a problem is a process of elimination. One of the possibilities more difficult to eliminate is root rot. Most gardeners believe that they cannot possibly know the health of a mature tree's roots.

Cankers on the stems, stem tip dieback, off-color foliage, early fall color and early defoliation are also clues that a tree may be stressed by underground causes. To detect the wood rots and root rots, look for mushroom-like fungi growing at the base of the tree or shrub. In wood rot fungi, the conks (also called shelf fungi or fruiting bodies) may be found growing on the trunk or main branches. These are signs of the disease. The actual fungus is probably growing in or on the roots, or inside the wood. One of the most common examples is Ganoderma root rot, which produces a shelf type of fungal structure at the base of many trees, especially honeylocust. The structure is reddish-brown and appears to have been varnished. Its presence indicates invasion by a root rot. Other fungi may indicate wood rots. Wet weather often triggers the formation of these structures. They could easily be confused with fungi growing on dead organic debris near a tree. If, however, they are growing from the tree itself, they are excellent signs of wood rot or root rot.

No chemicals help a tree in decline. Use approved cultural practices, such as proper watering and fertilizing to improve vitality. Cut out dead branches in the dormant season, fertilize in late fall or early spring and keep traffic off the root system. For very old or large trees, fertilization and watering may have no benefit, but these practices sometimes help the tree survive for years.

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