Abstract
Duncan grapefruit trees were inoculated with citrus canker. The spectral reflectance of individual leaves was measured and found to change as canker lesions develop. The spectral change was most pronounced in the 600-700 nm spectral region. Reference spectra were treated as vectors in a linear system, and the extent of lesion coverage was estimated. Performing a similar analysis with spectra from iron deficient, manganese deficient, and leaves with greasy spot symptoms showed the uniqueness of the spectrum of the citrus canker lesion and the potential for this technology for assessing the extent and magnitude of canker infection.