Specialist Tree Decay Detection

When a visual tree inspection identifies signs of potential internal decay — fungal fruiting bodies, unusual response growth, cavities, wounds, or areas of deadwood — further investigation is often required before a defensible management recommendation can be made.

Urban Tree Management provides specialist tree decay detection investigations using the IML Resistograph and Arbotom sonic tomography, giving clients and their tree surgeons accurate, objective data on the internal condition of trees across Greater Manchester, Lancashire, Cheshire, Merseyside, and nationwide.

Non-Invasive Decay Detection: Sonic Tomography

Sonic tomography is a non-invasive technique in which a series of sensors are placed around the circumference of the tree stem or branch. Each sensor is tapped in sequence, sending a stress wave across the wood to the remaining sensors. The time taken for the wave to travel between each pair of sensors is recorded and processed by specialist software to produce a detailed two-dimensional or three-dimensional image of the internal condition of the tree.

Sound, dense wood transmits stress waves quickly. Decayed, hollow, or structurally compromised wood transmits them more slowly — and the tomogram maps these variations in wave velocity to reveal the location, extent, and pattern of internal decay with a level of accuracy and detail that external inspection alone cannot provide. Urban Tree Management uses the Arbotom sonic tomography system, one of the most widely used and clinically validated tools available for this type of assessment.

The results of a sonic tomography investigation are presented in a clear visual format that can be shared with tree surgeons, local authority tree officers, insurers, and legal advisors, providing an objective and independently reproducible basis for any management decisions that follow. Where appropriate, sonic tomography findings are corroborated using micro-drilling or Resistograph testing to confirm the tomogram image with direct physical data.

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Invasive Decay Detection: Resistograph

The IML Resistograph is a precision instrument that measures the resistance encountered as a fine needle is drilled through the wood at a controlled speed. Dense, sound wood creates high resistance. Decayed, hollow, or structurally weakened wood creates significantly lower resistance — and the instrument plots these readings in real time as a resistance profile across the full diameter of the stem or branch.

Resistograph testing is used to measure the thickness of the residual wall in trees with suspected internal cavities or decay, to confirm the findings of a sonic tomography investigation, to assess the structural significance of decay identified in an initial visual inspection, and to provide baseline data for monitoring progressive decay over time. The technique is minimally invasive — the needle diameter is small enough that no lasting harm is caused to healthy wood — and the data produced is precise, repeatable, and accepted by local planning authorities and insurers as robust evidence of a tree's internal structural condition.

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Why Decay Detection Matters

Decay detection investigations produce information that cannot be obtained through visual inspection alone, and that is often critical to making proportionate, defensible tree management recommendations.

The data gathered allows Urban Tree Management to confirm or rule out internal structural failure as a risk factor, provide evidence to support or defend Tree Preservation Order applications and appeals, inform the management of aged, veteran, and high-value trees where retention is the priority, establish a measurable baseline for monitoring decay that is known to be progressive, provide evidence of structural integrity for insurance purposes, support local authority assessments of tree work applications, and give landowners objective evidence that their duty of care is being met.

In many cases, decay detection investigations allow trees to be retained with targeted management rather than felled — preserving valuable amenity, ecological, and heritage trees where a visual inspection alone might have led to a more cautious recommendation.