Q: What is wrong with this saguaro cactus?
A: The brown and black areas show signs of bacterial necrosis. This is a common affliction of cacti in the desert and unfortunately once it gets into the main stem and spreads that wide there is nothing you can do to fix the problem. Eventually the cactus will succumb and fall over. It would be wise to plan for that eventuality and make sure there aren’t any potential hazards such as the chance people or property could be damaged if it fell unannounced. Contracting with an experienced landscaper or certified tree professional to take it down would be appropriate if any hazards are present.
Peter L. Warren is the urban horticulture agent for the Pima County Cooperative Extension and the University of Arizona. Questions and photos may be emailed to email@example.com.