SPECTRAL REFLECTANCE CHARACTERISTICS AND DIGITAL IMAGERY OF A PINE NEEDLE BLIGHT IN THE SOUTHEASTERN UNITED-STATES

A field study determined an optimal approach for the remote sensing of a pine needle blight of unknown cause that occurs frequently in the s outheastern United States. Needle spectral reflectance was measured in five pairs of slash pines (Pinus elliottii Engelm. var. elliottii), e ach comprising a blighted and a nonblighted tree. Reflectance of bligh ted needles generally was greater within the 400-700 nm wavelength ran ge and less in the 720-850 nm range compared with nonblighted needles (p less than or equal to 0.050). The relative change in reflectance, o r reflectance sensitivity to the blight, was greatest near 680 nm. As predicted by the reflectance sensitivity, a black and white digital im age at 680 +/- 5 nm revealed strong contrast of a blighted compared wi th a nonblighted tree; the blighted canopy was nearly white in the ima ge, while the nonblighted canopy was dark grey. Contrasts were much le ss at 560 +/- 5, 694 +/- 3, and 700 +/- 5 nm, in the panchromatic visi ble spectrum (410-740 nm), and at 760 +/- 5 nm. Remote sensing of sout heastern pine forests at 680 +/- 5 nm ultimately could provide regiona l estimates of blight occurrence and distribution, and thus contribute to determining its cause.