I live in the San Francisco Bay area of California. My avocado tree is about 50 years old. It has produced for about 35 years, some years better than others. In our area we are experiencing our fourth year of drought. My avocado tree is slowly losing its canopy. For the last couple of years it has dropped excessive leaves and some new growth just dies back. I really don't water since it's so large I don't know where to start. We did change around the base of the tree a couple years ago by covering the area around the entire tree with large river rock, just for aesthetics.
Is there any suggestions as to my problem?