Reports of a saguaro disease, popularized almost fifty years ago, persist, but saguaros are not subject to blights. The saguaro is a long-lived cactus, most affected by long-term climate cycles of frost and drought. In actuality, the saguaro is a common plant in the Sonoran Desert, not an endangered species.
Without question, the biggest threat to the saguaro is our rapidly expanding human population. The development of new homes in the Tucson area has resulted in a tremendous loss of saguaro habitat. With this influx of people has come another threat to the saguaro-exotic plants. Exotic plants almost always out-compete native plants for the limited resources of water and nutrients. They have also led to an increase in wildfires, which harm or kill native vegetation, including the saguaro.