Q.Organ pipe cactus turning woody what can I do?
We just bought a place in Mesa AZ and have two organ cactus plants in an East facing area. I have noticed that the columns are turning to wood at the bottom, but is still green on top. What is causing this and is there anything I can do to help them. Since we didn’t plant these cactus I am not sure what care was taken when they were planted and for how long they have been here.

Probably just "corking", a natural aging phenomenon.
https://cactiguide.com/cactipests/#corking
From the photo, with the plant on the right, it appears excessive, but doesn't look like a fungus to me. Even if it is, there is not much you can do except adjust the watering to an appropriate amount, and avoid sprinklers hitting on the stems.
By the way, there appears to be two different types planted next to each other, maybe two species of the genus Stenocereus. I'm not a cacti expert even though I grew up in Scottsdale with a horticulturist father who was on the board of the Desert Botanical Garden. If you want to get into it, you can visit that great resource or use the online cactiguide.com