Using Remote Sensing to Distinguish Common (Isocoma coronopifolia) and Drummond Goldenweed (Isocoma drummondii)

Common and Drummond goldenweed are troublesome subshrubs that often invade rangelands in southern Texas. Both species produce a profusion of conspicuous golden-yellow flowers in the fall. Common goldenweed flowers from late September to mid-October, whereas Drummond goldenweed flowers from mid-November to early December. Plant canopy reflectance measurements made on both species showed that they had higher visible (0.63- to 0.69-μm waveband) reflectance than did associated plant species and bare soil during flowering. Flowering common and Drummond goldenweed plants had a yellow image on conventional color (0.40- to 0.70-μm) aerial photographs that made them distinguishable from associated plants and soil. Computer analyses of the conventional color film transparencies showed that common and Drummond goldenweed infestations could be quantified from associated vegetation and soil. Flowering common goldenweed plants could also be detected on conventional color aerial video imagery.