Decay dectection equipment

[Marcus B-T]

Just seen this is escalating into the usual debate about decay detection equipment. The big problem is training and information about how things work and limitations in what they detect. Hopefully the person using the equipment is trained to use it properly, even if it is a hammer.

 

That is why as a company we have invested so much time and effort (6 years and well over 20,00 trees) into understanding the limitations of thermal imaging and providing full training and aftersales support. We even offer training to potential clients of thermal imaging so that they can also understand the process and raise concerns directly with us if they feel the technology has been missused. But the bottom line is no one should fell a tree without making a full internal inspection beforehand that confirms findings. It is madness not to do so even if you use a hammer. It only takes about 10-20mins with an increment borer and if you are going to fell it anyway the argument about damaging the tree goes out of the window.

 

There are a number of processes such as wood drying prior to infection that people are blissfully unaware of. They fell the tree and think there is nothing wrong with it when it could have a very serious area of decay at a point remote from where the tree was cut. The biggest problem is that most people when things go wrong say 'oops, oh dear never mind' and walk away putting it down to experience rather than trying to understand why it was not as it seemed. Having looked at over 20,000 trees I know things are not always as they seem to the human eye. You need to think carefully about the processes going on in the tree before felling it so that when it comes down the owner knows what to expect.

 

SO, the biggest limitation to all pieces of decay detection equipment (including hammers) is?

 

They are all used by humans!

[stevelucocq]

Brilliant!! they do not teach you this sort of stuff on the course. cheers for everyone thoughts

[John Hancock]

I’ve found the Picus useful for the following reason…

 

All of our parks and even the cemeteries have ‘friends’ groups and although they are very useful in some respects, can prove challenging from time to time. I’ve found the Picus very useful as the Tomograph can be added to the written tree report and presented in a form that most people can understand.

 

We have removed trees in the past and come under a lot of ‘post-felling criticism’ from the local press; this is mainly due to a lack of information and a poor understanding from the general public. A Picus or to a lesser extent, a Resistograph can help alleviate that.

 

I should note however that in every case the Picus was used, I already knew or had a ‘gut-feeling’ what the result was going to be.(I guess this comes with experience, an enthusiasm for examining slabbed-up sections of wood and a knowledge of fungi).

 

The cross section pictured is not an accurate representation of the decay as this section was a good 1.5 feet from ground level.

 

So in summery,

 

Picus – An excellent bit of kit that can be used to produce a comprehensive, colourful tree report that can be understood by a wide variety of people, (but don’t rely on the Tomograph alone).

[Will Hinchliffe]

I am also studying for the tech cert but have little experience with decay detection. I'm going to add my bit though because it is good for a bit of exam preparation.

 

There are limitations with all devices marketed as decay detection devices. It is important to understand that most do not actually detect decay.

 

Decay detection devices are mostly used to make an estimate of the dimensions and quality of residual wood where a cavity is suspected. Many other factors must be considered to determine acceptable residual wall dimensions for tree retention. The limitations of the internal investigation techniques must be fully understood by the user to allow an accurate report to be completed. To overcome the problems of individual decay detection devices two investigations using different methods are often used.

 

A core sample can give an accurate measurement of the residual wall at the point it is taken but it is necessary to take multiple samples to get an estimation of the shape and size of the decay pocket. Core samples are invasive but allow for inspection of reaction zones and growth rates. A fractometer can be used to measure the bending angle and force required to snap the core sample but to expand on this measurement to give an idea of overall tree stability requires consideration of so many other factors that it is not practical.

 

Drilling with a 4mm bit is invasive but can yield a range of information. Resistance to progress of the drill bit is felt and interpreted by the user. Shavings can be collected at measured depths and can be investigated further.

 

Acoustic testing (mallet) can indicate the presence of a cavity and its location but further investigation is often required to justify retention of a tree with potential targets.

 

Shigometers (and Vitalometers) measure electrical resistance across two points very close to each other. Resistance is higher in healthy cells, decayed cells have a higher concentration of inorganic salts. The probe can be inserted into a drilled hole and the resistance measured at intervals. Changes in readings may indicate decayed wood. Dry decays can give false readings. The Shigometer is not widely used.

 

Digital microprobes measure the resistance to penetration of a 1.7mm blunt probe. The resistance is recorded graphically and digitally. The resistance to penetration is measured very accurately and growth rings can be detected. The problem is that the probe does not always go in straight and may bend. Multiple measurements must be taken.

 

Resistographs measure resistance to Torque of a 3mm probe with a cutting tip. Early detection of Ketzshmaria deusta is often missed. Widening of growth rings provides less resistance to the cutting bit and this can be misinterpreted as decay. Deflection of the probe can also occur. Fungal colonisation through the breached reaction zone has been shown to occur so this should be considered an invasive technique.

 

The Picus measures the speed of the leading edge of a sound wave as it travels through the tree. By using multiple sensors a matrix of sound attenuation is recorded. Using the speeds relatively computer software is used to create a map where colours are used to show areas of different sound attenuation. If a stem is evenly decayed the software may show the whole of the cross section as healthy wood. Ring shakes can also distort results.

 

Thermography uses an infared camera to detect the surface temperature of the tree. Uneven heat distributions are associated with degraded tissue or cavities. This system does not provide an estimation of residual wall thickness, but may help in targeting other investigations.

 

 

 

Would you include anything else in the decay detection topic? Tree statics, VTA ?

 

Please feel free to point out any false statements I have made and any criticisms.

[Bundle 2]

Following from subject areas mentioned by Marcus...I tend to agree that tree management decisions are sometimes far too prescribed by recipe formula...and some frankly poor management choices made as a result....but that this emotive statement can be remedied by way of appropriate investigation...Only the professional in you can determine this level of resource for the individual cases...needless to say I'm sure we will all have a different take on the same situation.... I digress...Steve:

 

On wound and wood drying...an axtract from Shigo's work " The Man!! "

 

http://www.google.co.uk/search?q=shigo+wound+closure&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla

 

http://www.google.co.uk/search?hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&hs=mez&q=shigo+crack+drying&btnG=Search&meta=

 

and from Mattheck's work....

 

 

Sorry but I have a problem with invalid file blah blah....so I can only tell you search " Mattheck drilling decay " in google and find the right document a pdf file and such....

 

I hope you find this helpful!!

 

Phenom, as was intimated earlier, different methods yield different results and highlight additional aspects as you too are saying...I think of Kretzchmaria in this dimension....and people need to think again as Marcus said , about the method used and why....It worries me a bit that folk say " a couple of mins with tree officer and a tap here and there...." This is not a decent management process and will be criticised for its laxidasical expression....I very much hope the reality is somewhat different.....!

[christreeroot]

It worries me a bit that folk say " a couple of mins with tree officer and a tap here and there...." This is not a decent management process and will be criticised for its laxidasical expression....I very much hope the reality is somewhat different.....!

 

This wasnt well worded i agree...

 

The problem is with all these decay detection methods is the finance involved, trees are not classed as a priority by the general public and even in LA's trees are always low down the pecking order when it comes to handing out budgets.

 

I do like the look and idea of the Thermal Imaging But and its a very big BUT, the cost of equipment and training means that inspection prices are high and will never compete with a VTA and GIS prices so it may ultimatly fail as a system due to costs, even more so at the moment when budjets are being set.

 

We often suggest trees for further investigation by the picus etc, the take up on these recommendations when they find out the price is below 5%.

 

" Chris, why would i pay that for further investigation when i can just remove it now for the same price...."

 

I hate to be the one to say it as i love trees and wish to save as many as i can from uneccesary removal but trees are way way down the pecking order in the domestic, GVT and commercial sectors. The majority of the time the cheapest route will always be taken.

 

We carry out tree surveys of 10,000 + trees for a number of charitys, LA's and comersial clients, everyone has asked us to cut down survey costs to a minimum, even if this means missing out huge areas.

[stevelucocq]

I am also studying for the tech cert but have little experience with decay detection. I'm going to add my bit though because it is good for a bit of exam preparation.

 

 

Again, great cheers. This is pretty much similar to the areas I have covered. Reading about other peoples views and knowledge is helping to get a better understanding of the whole process. cheers for everyones input.

[Yorkshireman]

Steve,

 

.

 

If when budget allows, I will be seeking training and/or bringing in Thermal Imaging.

 

 

 

.

 

 

Well when you do Dave

Give me a ring

[Amelanchier]

I have used every item out there and nothing comes close to a nylon hammer, and an experienced ear.

 

Every item??

 

Attached .pdf is a decay detection list from “Wood and Tree Fungi: Biology, Damage, Protection and Use.” by Schmidt 2006 found in “Diagnosis and prognosis of the development of wood decay in urban trees” by Schwarze 2008.

 

How did you find the gamma ray computer tomography? Or the sniffer dogs?

 

Table_2_Diag_&_Prog_Schwarze_2008.pdf

[David Humphries]

Well when you do Dave

Give me a ring

 

Will do Iain.

 

Trying to put something together with Andrew Cowan at some point during this New Year.

 

 

I'll give you a bell

 

 

 

 

 

 

.