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Why is My Oak Tree Losing Bark?

Hamilton County Extension Agent Tom Stebbins has been getting quite a few calls lately about bark falling or coming off mainly white oak trees.  Although many of these calls are coming from Signal Mountain, the problem is not confined to that area.

According to these callers, there is too much fallen bark to blame squirrels, birds or insect borers.  Callers describe the situation to Tom as “It looks like a bear hugged the tree and pulled the bark away.”  Based on this description, Tom thinks the culprit might be the fungus Aleurodiscus oakesii and the condition is called “Smooth Patch Disease of White Oak.”

As you may recall from Biology class, fungi are neither plants nor animals and perform an essential role in the food chain—fungi break down dead organic material and therefore cycle the matter back into the food chain.  Unlike mushrooms, the iconic fungus fruiting body, the Aleurodiscus species produce a flat crusty fruiting body that is rarely more than a centimeter (half inch) in any direction and usually about a millimeter or two thick.  However its effects can be seen from quite a distance.  Although A.oakesii is not a parasite, it lives on the bark of trees, primarily oaks and other members of the Fagaceae, such as chestnut, although it is found commonly on many other hardwoods.  The food source for the fungus is actually the dead bark of the tree.

Is this condition a problem?  According to Tom, the fungus is not pathogenic to the tree.  In other words, the fungus will not kill the tree–it just goes after the bark layer and causes it to fall off.   It looks bad but no control is suggested—no sprays for insects are warranted unless high populations are visible.  Just consider this a case of natural recycling.

More information about this condition can be found at this link: http://botit.botany.wisc.edu/toms_fungi/apr2006.html

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