Pubescence Affects Spectra and Imagery of Silverleaf Sunflower (Helianthus argophyllus)

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Abstract
Silverleaf sunflower (Helianthus argophyllus Torr. & Gray) is a weed in the sandy soils of south and southeast Texas. The young plant parts are densely white-tomentose. This pubescence greatly increased laboratory and field-measured light reflectance over the 0.5- to 2.5-μm waveband compared with the sparsely-hairy leaves of common sunflower (Helianthus annum L.). This increased reflectance caused silverleaf sunflower's image on Eastman Kodak Aerochrome infrared color type 2443 film to be “pinkish” compared with darker magenta images for other plant species. Therefore, aerial photography may be useful to distinguish silverleaf sunflower plants from other plant species to locate its endemic areas, monitor its spread, and delineate areas needing weed control.