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Sunday - May 24, 2009

From: Austin, TX
Region: Southwest
Topic: Trees
Title: Should hole in escarpment live oak be filled in Austin?
Answered by: Barbara Medford


Regarding one of my mature escarpment live oaks: should an old hole (about 8" across) in the trunk (caused by the improper cutting of a branch) be filled? A tree service technician advised me that he should fill it in as the hole could fill with water and rot the tree. This hole has been there quite a while. Please help.


We're not very clear about the character or cause of this "old hole" in your Quercus fusiformis (plateau oak). Are you saying that a branch was cut off and the hole formed by rotting or some other deterioration? A trimmed branch should be cut pretty flush with the trunk of the tree, and painted immediately with a paint for that purpose to help deter the entrance of Oak Wilt fungus, especially in the months of January to May, when the nitiludid beetle is active. In fact, no trimming at all should be done during those months, and damage to the bark or branches should always be avoided. Is it actually a hole opening into the interior of the trunk, or just a depression where it healed over? Either way, we can't diagnose the problem from a distance, but the filling it in (with what?) to keep water from filling the hole and causing rot sounds a little strange.  If the person who recommended this is a licensed arborist, and you have confidence in his advice, ask him what he proposes to fill the hole with.

We found a website from AllExperts Trees-hole in oak tree which describes the various ways holes can be caused in trees and some now disproved theories about what to do about those holes, including filling the cavity. You should read the whole article and especially note this excerpt:

"How should trees with cavities be treated? Recent research shows that it is better to leave the cavity open - remember no type of drainage, sterilization, fill material, wound paint, or scraping treatment stops decay - and simply take the necessary measures required to improve the overall health of the tree. A healthy tree has the strength to compartmentalize and wall-off decay." 

Before you agree to any treatment of your tree, we suggest a "second opinion."  You need someone who has been trained in care of trees, a licensed arborist, to look at it and make recommendations. Perhaps the Travis County Extension Office can recommend someone or at least what certifications they recognize. Go to this Texas A&M AgriLIFE Extension website for Travis County. It has contact information and they are trained to help you with this kind of problem.

Quercus fusiformis

Quercus fusiformis

Quercus fusiformis

Quercus fusiformis



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