What causes an ocotillo’s leaves to turn yellow?

Question

It has been healthy and producing flames regularly for 8 years. The conditions have not changed.

Answer 1

Yellowing leaves could indicate watering issues, to much or to little, nutrient concerns and possible insects.

Scale can become an issue for Ocotillos and they are a sucking insect.

The use of an insecticidal soap should clear them up.

Here is a link to refresh you on the care requirements.

https://www.gardeningknowhow.com/ornamental/cacti-succulents/ocotillo/ocotillo-plant.htm