Digging and pulling buffelgrass is hard work. Rounding up volunteers can be difficult and in many parts of the Sonoran desert the plant is spreading faster than it can be removed. Where it forms large patches, or grows in fields of large rocks or on steep slopes, digging and pulling may be impractical and even dangerous. That's why Saguaro National Park did some spaying from a helicopter after extensive testing to prevent drift (which was virtually nonexistent as measured by white cards placed at varying distances from the spray site to register spots of blue dye in the spray) and to minimize harm to native plants (which are doomed anyway if they're in or near a buffelgrass patch). It worked. But buffelgrass seeds can live for years, and when the Park Service's funding was cut the spraying ended, and the buffelgrass returned. The herbicide used was glyphosate which breaks down within a few weeks at most and thus poses no threat to people visiting the site.