The correct amount of water to apply depends on the size of the plant and the number of days between irrigations.
Local Columns
It can be confusing to tell the difference between abiotic and biotic diseases just with your eyes. Plant disease symptoms are typically not very specific.
When to water next depends on the tree. Desert trees allow for soil to be dry between waterings. But trees from wetter climates can’t tolerate such dry soil.
We initially thought it was sun scorch. But patches have also appeared on the sides of the saguaro that get little direct sun.