Saturday, June 30, 2012

To continue my series on tree decay, I've prepared some facts about potential tree decay indicators versus positive tree decay indicators. This is very useful information on decay and what to do about your tree decay.

Potential Decay Indicators

The number of potential indicators is considerably larger than positive indicators because they are based on the biology of decay in living trees and decay impacts on structural health. Potential indicators are important in decay assessment because relatively few trees with decay have positive indicators. In my research on decay, more than half of the trees I identified to have decay in the lower trunk, yet only very few had positive decay indicators. Therefore, it becomes necessary to rely on potential indicators to help identify trees that might have decay, but do not have positive indicators. 

Potential indicators typically require an additional assessment to confirm if decay is present in the tree. Potential indicators can be placed into two broad categories. 

The first group is the presence of wounds or other damage that has exposed the sapwood or heartwood, such as pruning wounds, loose or missing bark, lightning strikes, or cankers. Wounds are common infection sites for decay fungi, and most wound infection occurs via airborne spores that are released from conks or mushrooms. Most small wounds can be sealed over by a tree before they become infected. Larger stem wounds are twice as likely to become infected and decayed than the smaller wounds.  Oozing sap or liquid in deciduous trees or resin flow in conifers may also be a potential indicator of decay because they identify sites of old wounds. 

The second group of potential indicators is symptoms associated with the loss of wood strength, such as partial wood failure and response growth patterns. Cracks in the bark or sapwood due to wood failure, and ribs that originate in decayed wood are common in trees weakened by decay. A more subtle indicator is response growth that results in bulges or swelling in branches or the stem. Response growth is a mechanical and physiological process where a tree reacts to the loss of wood strength and movement at the cambium. Response growth may result in an increased quantity and quality (strength) of wood being produced by the cambium. 

Another decay indicator is the exposure of the inner bark from increased secondary response growth similar to that which occurs on young trees that are increasing faster radially than the outer bark is expanding.  See the picture below for an example.

Indicators for Root Decay

Positive indicators for fungi that decay larger tree roots are primarily the same as those seen in stems, except the fungal fruiting bodies are attached to the roots. Cavities, conks, or mushrooms at the base of a tree often indicate root decay, because many of the fungi that cause butt rot also decay roots. A few decay fungi may fruit on woody roots at an extended distance from the tree trunk, but in all cases they are attached to a woody root.

 Arborists should be aware that many non-pathogenic fungi also fruit as mushrooms from the soil near the base of trees, including beneficial mycorrhizal fungi. Potential indicators of decay or loss of woody roots are inherently different than the decay indicators in trunks and branches. Poor tree crown health can be an indicator of the presence of root decay. Symptoms include chlorotic, sparse, or undersized foliage, small and/or large branch dieback, and reduced growth rates. Because root decay fungi can spread from root-to-root contact and vegetative fungal growth through the soil, root decay centers may develop. These root decay centers may result in clusters of trees that have failed as a result of root and butt rot, and indicate that adjacent trees may also be affected. Response growth patterns at the base of a tree, such as swellings, bulges, or absence of normal root flare development, are common in trees affected by butt and buttress root decay. These changes in normal trunk taper are more common in large diameter older trees.

Physical changes on the site that have wounded or damaged roots are another potential indicator of root decay. Evidence of fill or grading around trees, the lack of a normal basal root flare, or the wounding of exposed roots may suggest root loss or decay. Visually evaluating buttress and larger diameter roots is challenging, even if the tops of roots are exposed, because most root decay develops from the bottom of roots.

If you are concerned about the condition of your trees, it is best to consult a professional.  Your local tree service or a certified arborist will properly assess your trees.  The professional staff at Trees "R" Us, Inc. is highly qualified in tree care and maintenance.  We have 4 certified arborists that have been trained in identifying tree decay and will provide you with the best, most accurate advice about your plants and trees.

Stay tuned for information on the severity of decay and what to do about it.

Trees "R " Us, Inc. is proud to educate our communities on proper tree care and maintenance.

It is through education that we really save trees and help the environment.  We hope you found this post informative and educational. 
Trees "R" Us, Inc. is a professional tree service for the Chicago's North Shore, North and Northwest suburbs.  Tree trimming, tree removal, stump grinding, fertilizations, tree disease treatments and prevention as well as plant health care are just a few of our high quality, professional services.  Contact us today for a free analysis or quote at or at 847-913-9069.
Thanks for reading,

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