Abstract
Two hyperspectral remote sensing techniques, spectral reflectance and chlorophyll fluorescence, were used for the identification of biotic stress (sharka disease) in plum trees at an early stage without visible symptoms on the leaves. The research was focused on cultivars that are widely spread in Bulgaria: ‘Angelina’, ‘Black Diamond’ and ‘Mirabelle’. Hyperspectral reflectance and fluorescence data were collected by means of a portable multichannel fibre-optics spectrometer in the visible and near infrared spectral ranges (400-1000 nm). Statistical and deterministic analyses were applied for assessing the significance of the differences between the spectral data of healthy (control) and infected plum leaves. Comparative analyses were performed with complementary serological test DAS-ELISA, broadly implemented in plant virology. The strong relationship that was found between the results from the two remote sensing techniques and serological analysis indicates the applicability of hyperspectral reflectance and fluorescence techniques for conducting health condition assessments of vegetation easily and without damage before the appearance of visible symptoms.