Evaluation of a portable MOS electronic nose to detect root rots in shade tree species

The early detection of wood decays in high-value standing trees is very important in urban areas because mitigating control measures must be implemented long before tree failures result in property damage or injuries to citizens. Adverse urban environments increase physiological stresses in trees, causing greater susceptibility to attacks by pathogenic decay fungi. The detection of fungal root rots in urban trees is particularly difficult because conventional detection tools, currently used for diagnosis of wood decays, are not feasible below ground level. Portable electronic olfactory systems or electronic noses (e-noses), currently used in many different scientific fields and industries, previously have been tested for the early diagnosis of wood decay fungi and wood rots. We evaluated the accuracy and effectiveness of the portable PEN3 electronic nose to discriminate between healthy and decayed root segments of five shade trees species, artificially inoculated separately with three species of root-rot fungi and incubated in different soil types under laboratory conditions. The PEN3 e-nose discriminated between healthy and inoculated root fragments and between different decay fungi in different soil types for most host-fungus combinations, but the discrimination power of this e-nose varied depending on tree species and strain of root-rot fungus analyzed. We provide explanations for the ineffectiveness of the e-nose to detect low levels of decay for certain host-fungus combinations. The advantages of e-nose detection over conventional wood decay detection tools also are discussed