Lesions caused by insects feeding on plants are associated with the generation of regions of blue-green fluorescence in such as the cotton boll carpel wall and in the lint region. The present disclosure now provides methods and devices to rapidly and non-invasively detect and measure the insect-related fluorescence and relate the fluorescence generated to the likelihood of insect damage in a crop. In particular, the methods are related to stink bug damage in the cotton plant, but are also suitable for the detection of insect-related damage of any plant. The methods of detecting insect-induced damage in a target plant tissue may comprise exposing a target plant or a fragment thereof, to an ultraviolet or violet light; and detecting an ultraviolet light-induced fluorescence from the target plant or the fragment thereof, thereby indicating the presence of insect-related plant damage. Further provided are devices configured for the identification of insect-induced damage in a plant or a fragment thereof, comprising: a source of an ultraviolet or violet light, at least one light detector; an electronic system for converting an output electrical signal to a measurement of the intensity of fluorescent light detected by the detector; and an output system to convert the measurement of the intensity of the fluorescent light to an indicator for indicating that a target plant or fragment thereof has insect-induced damage.