What are your feelings toward the use/application of the resistorgraph in determining a hazard tree

B. Smith

Reply to post by Brian Smith, on September 11, 1998 at 20:55:46:

The resistograph is seen by many as one of the better diagnostic tools available, as opposed for example to the arborsonic, however, these are simply tools to aid the inspectors visual tree assessment (VTA). It is very often difficult to compensate for experience and knowledge. Personally I go with the VTA every time.

Paul

Reply to post by Brian Smith, on September 11, 1998 at 20:55:46:

We have the M series (not F), and find it to be a helpful and useful tool. Mind you, it cannot determine hazard. It is one method by which to evaluate extent of decay, and based on other tests and evaluations of site, tree, exposure, target, ect. evaluate hazard.
Larry Costello has led a research project that evaluated the effectiveness of the Resistograph and battery-operated drill in detecting decay. He tested two species: blue gum and elm. On elm, the decay detection accuracy was 100%; on blue gum, less. In both species decay could be detected with similar accuracy with Resistograph and drill (depending on the operator, however).
Like all testing tools, you have to develop familiarity with the species and how to interpret the information generated. Once you know how to interpret the graphs, it is quicker than drilling, and provides a record. The drill, however, can be just as accurate if you train yourself well, and it is much cheaper!

Reply to post by Brian Smith, on September 11, 1998 at 20:55:46:

How can an invasive method be a "good" tool, we say don't drill drain holes in cavites because your breaking the CODIT boundry, but now we bore a hole to see if there is one.

has anyone done disections on trees that were resistographed years ago?

jps

Reply to post by John P Sanborn, on September 11, 1998 at 20:55:46:

John, Personally I don't mind too much using invasive methods on trees, and that includes taking increment cores, drilling- and if I had a ($$) resistograph, I'd use it often. Sometimes I even chop into roots (usually when no one is watching) if I need to see what it looks like inside.
It seems like a crazy thing to disrupt chemical barrier zones, possibly exposing un-infected wood to parasites, but parasites use their own routes, including embedded branches, to move around. Also, the trees have quite an arsenal of defense strategies.
To respond to your question, I dissected a Douglas-fir tree that had been cored a few years earlier, and the wound was covered completely by new incremental growth. No decay or discoloration was associated with the wound. I have a slide of that. Regards, Peter

Reply to post by Brian Smith, on September 11, 1998 at 20:55:46:

I have an F500 and love it. As Nelda points out, it is just one tool available, but for the first time I am able to read tree conditions to a depth of 50 cm and that is very important round my way, where the trees are often more than 1 metres in diameter. As always with such instruments, there is room for improvement, but having been over to the IML factory earlier this year, and seeing how they are made and the test data available, I am increasingly confident with my own records.

Julian Dunster

Reply to post by Peter Torres, on September 15, 1998 at 20:52:57:

Peter, did the core invade previously decayed wood? That would seem to be the real danger in using invasive techniques- when there is an actual barrier, and decay that could spread outward.

I tend to agree with you on using these techniques. We are much like the medical profession was not so many years ago. We haven't yet got all the nifty (and expensive) equipment they have to be non-invasive, but we're working on it! In the mean time, we have to know. If I know, as aprofessional, that there may be decay inside a tree, but do not make the effort to find out how much and where, I can only make one decision- take it down! Failure to do so would leave the possibility of that tree failing, and causing injury or damage. In fairness to the customer, it is much better to know what you are dealing with. Would a doctor say "I think it's cancer, but you might get an infection if we operate to find out, so let's just leave it alone"? That seems irresponsible to me.

I don't advocate drilling every tree, or without justification. But the information gained far outweighs the damage inflicted, especially if you perform with care and skill.

Russ

Reply to post by Julian Dunster, on September 11, 1998 at 20:55:46:


Do you feel as a consulting arborist, confident in your ability to assess and evaluate potential hazard without the aid of archaic and invasive mechanisms ?

Paul H.

Reply to post by Paul H, on September 16, 1998 at 15:15:50:

Short answer: a hearty NO!

Long answer: I am often left with my intuitive sense in a final recommendation to a client regarding the hazard potential of a tree. It is unfortunate that such final determinations are also often (albeit necessarily) influenced by the litigious character of our society (US).

Even with current technology (e.g., resistograph), there are substantial limitations to what we can know about a tree, and even what it means once we know it!

The resistograph is an important step in the effort to improve this situation so that we might make more informed decisions regarding to preserve or condemn a tree.

Like all our investigative and maintenance efforts, we must weigh the benefits, both to the tree and the client (and others), versus any negative impacts of our techniques.

Consider that one of the most invasive techniques employed by arborists is pruning!

It is my opinion that a tree of reasonable vigor (vitality?) will easily compartmentalize the very small wound created by resistograph or other drilling (1/8"+/-). Increment boring... significantly larger and should therefore be used with even greater discrimination.

In short... the end must justify the means.

Torrey

Reply to post by Paul Hawksford, on September 11, 1998 at 20:55:46:

Hi Paul,

You must have prayed that I missed this little comment. Yes the Arborsonic
has its limitations. It does not differentiate shakes and splits from decay
and if used incorrectly can be useless but it is the next step we are seeking!

It need not be invasive and it never goes through barrier zones. It unfortunately
does not have somone like Klaus behind it. But none the less a valuable diagnostic tool.

Mark

Reply to post by Mark Hartley, on September 12, 1998 at 18:14:05:

Dear Mark

My apologies, I didn't mean to exclude you from the discussion. I tend to relate more readily towards identification of potential hazard through field evaluation experience over many years as opposed to "drilling holes." Subjective, though its important to discuss all potential parameters.

On another note, I must also apologise to Phil about my comments regarding the "Arborsonic", we never did get chance to mend fences at last week's Arboricultural Association conference in Scotland. Let me have your details Phil and I will apologise personally.

Paul

PS. You can catch me at the APF show this coming week in Richmond, Yorkshire UK. I shall be there for three days. The drinks are on you!!

Reply to post by Torrey Young, on September 19, 1998 at 19:22:56:

Torrey

Thanks for the NO!

Though I disagree!

What are the legal precedents. Have tool aids contributed in providing definitive evidence in the US courts? What was the outcome and where can we access the legal data.

Paul

Reply to post by Paul H, on September 16, 1998 at 15:15:50:

Perhaps I missed something Paul, but doesn't medicine use invasive surgery
isn't this equipment qite modern and how do you suggest we detect decay from such interesting
sybiotic combinations as termites. I am not saying I like invasive techniques, it is just that
you don't seem keen to use any diagnostic tools. Pehaps decay is not of concen in the UK or
perhaps there is no litigation.

In all cases we should be encouraging the refinement and inprovement of diagnostic tools. The resistograph
is an improvement on the shigometer for decay detection, but a Shigometer is a valuble diagnostic tool
for determining vitality.

Reply to post by Mark Hartley, on September 19, 1998 at 19:22:56:

Dear Mark

Are you saying that without diagnostic tools, we are unable to detect the presence of decay in trees? I inspect many trees each week, and have done so for many years, I have yet to be proved incorrect in my diagnosis of decay or ill health in numerous plant species. Experience is one hell of a diagnostic tool! Subjective as the matter may be, are you saying we are encumbered in our ability to detect decay without invasive instruments? I don't think so.
Maybe we need to put it to the test sometime.

Regards

Paul H.

Reply to post by Paul H, on October 11, 1998 at 07:26:53:

Paul,

I am saying without question there are many instances where
decay give no obvious outward signs. This includes but is by
no means limited to such things as termite activity (perhaps
in palms for those who have them or oaks for those who don't)

There is no question that both the ultrasound and resitograph
provide quantitative data about the extent of decay at the point of
inspection. this information allong with good physics and matterial
engineering can and does give us the most definitive answers for
hazard assesment.

These tools are not a substitute for good training or experience.
They are instead valuble measirng devices that brovide vital information
rather that guess work.

I fail to see how anyone can see an enclosed basal cavity or the extent
and dimentionns of decay using just a trained eye. This is a profession
and as with all engineering professions (and thats what hazard assesment
is) it requires measurement. Sure a structural engineer may be able to say
a building will fail just by a cursory glance because of years of experience
but what makes these people wonderful is they can prove why at a theretical
level.

I agree these tools do not do that. Nor does an engineers tape measure or tables
they are just tools and is about time we got serious about using them. If we don't
I believe we leave ouselves open to subjective opinion and in the long term litigation.

The mark of the professional is knowing where when and why they should be used

Your thoughts Paul

Respectfully

Mark