Development of a novel approach for detecting wood decays in living trees using gas-sensor arrays

Wood rot is a serious fungal disease of trees. Wood decay fungi penetrate and gain entry into trees through pruning cuts or open wounds using extracellular digestive enzymes to attack all components of the cell wall, leading to the destruction of sapwood which compromises wood strength and stability. On living trees, it is often difficult to diagnose wood rot disease, particularly during extreme weather conditions when trees can fail, causing tree parts to fall onto people and property. Today, tree stability evaluation and inner decay detection are performed visually and by the use of commercial instruments and methods that are often invasive, time-consuming and sometimes inadequate for use within the urban environment. Moreover, most conventional instruments do not provide an adequate evaluation of decay that occurs in the root system. A long-term research project, initiated in 2004, was aimed at developing a novel approach for diagnosing inner tree decays by detecting differences in volatile organic compounds (VOCs) released by wood decay fungi and wood from healthy and decayed trees. Different commercial electronic noses (ENs) were tested under laboratory conditions and directly in the field, on healthy and artificially-inoculated stem wood chips, and root fragments. For the final stage, soil air was evaluated for the presence of VOCs released by root-decaying fungi on diseased standing trees cultivated in the urban environment.