UKTC Archive

Re: Throw away your resistographs

Subject: Re: Throw away your resistographs
From: Julian Dunster
Date: Dec 12 2008 15:09:33
There has always been concern about the effect of drilling, coring etc. Mattheck's research suggests that it is not a big issue, and in a few dissections I have undertaken, years after drilling, I did not see pronounced decay emanating from the drilling points.

There is always a trade off. Visual assessment suggests internal decay. You could apply a PICUS and map decay that way, but this may not be accurate enough as it often has troubled defining edges of decay zones. If the need to know more exact amounts of decay are paramount, then drilling resistance tests will provide the most accurate data. That creates a small wound. If you avoid wounding and recommend retention, and the tree then fails, you may have a problem. If you drill and derive a much more accurate answer, which then better informs the retain/remove decision you have been more diligent, but yes, there may be minor side effect. The accusation of wilfull damage would surely be an extreme overreaction. The effect of drilling is also going to depend upon species of tree, species of pathogen, and the overall vigour of the tree.

The analogue is in medicine - Doctors proceed through increasingly detailed levels of tests, and eventually, the test become increasingly invasive in order to know for sure what is happening inside the body. If they avoided the invasive tests they might make a wrong dioagnosis.

As technology gets better we should expect to see more debate about all this stuff. Right now, fear about drilling effects seems to be overrated.


Durkan, Paul wrote:
Extract from a tree report:
"0 - 10cm:- sound wood, with increasing resistance;
10cm: greatly increased resistance;
10 - 40cm: decayed wood, with low resistance"
Yes, at 10cm you drilled through wall 4 of the CODIT model, the chemically
and structurally altered (chemically resistant and strengthened) wood, that
was restricting the fungus to the "heartwood." Now the fungus might escape
into the sound and biologically active wood laid down in the years after
injury, possibly even be transported around the tree by the vascular system.
Suppose this was a TPO tree, in reasonable health and dealing with the
decay, might this constitute "wilfull damage"?
The German mycologist chappie speaking at last year's TEP seminar (November
07), was adamant that we must strive to not damage intact parts of trees
with such probes; that we must use other methods to assess decay.
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