Decay detection - further investigation
In some cases it is not possible to fully assess the condition of a tree by visual inspection. Decay in trees caused by fungus and bacteria can drastically reduce the strength of the wood, leading to failure of branches or entire trees which could cause severe damage to people and property. Decay is often visible through cavities or tears in a tree's branches or indicated by a fungal fruiting body on the bark or mushrooms at the base of the tree.
Understanding the extent and type of decay present is necessary to determine the safety of the tree. However, the extant of the decay cannot always be determined visually. In such cases there are a suite of decay detection techniques available to assess the nature and extent of decay so that appropriate remedial measures can be taken.
Examples of decay detection techniques include; sonic tomography which measures the relative propagation of sound waves through healthy and decayed wood; micro drill which measures the differential resistance of healthy and decayed wood to a narrow-bore drill; and Fractometer, which measures the bending stiffness and strength of a core sample taken from the tree. Such techniques are typically used in the management of protected and/or particularly valuable trees where evidence-based justification of any remedial measures is needed by the local authority tree officer.
Occasionally, owners of protected residential trees may also be required by their local tree officer to carry out these kinds of investigations.