could you please explain a little more so that others can help you.

Is it indoors or out?
What type of soil is it in? From this picture it' looks to maybe be in a landscape?
How often do you water?
How long have you had it?

I see your new.. WELCOME!! :-)

Also, what zone are you in or state?

Apologies for my newbie errors and thanks for the chance to clarify.

This is planted outside in Palm Springs (Sonoran desert zone 9).

It's sandy soil and been in the ground for 10 months.

Watered once a week for 10 min on a drip emitter

Gets direct sun in the afternoon

I note that the problem is preferentially affecting stalks on the left side of the plant, though don't know if that's significant.

I'm posting a picture of the whole cactus.

Any other info I can provide, cactus-friends?

Thanks for your help on this...

There's some sort of virus, at least in that limb, but I see potential trouble in other limbs, or think I do. Can we have some close-ups of the whole plant?

No apologizes needed! and you have some of the best help there is here already. :-)

I'm impressed with the speed of response and interest in helping out on this board!

Here's a closer shot of 2 of the problem limbs (in the back) and some healthy limbs in the front.

I'm not sure if there's a way to post multiple pictures per post?

Other areas have some nice looking new growth (posting this just to show I'm not a monster ;)

Hi trouble,

I wonder if the foundation corner is effecting soil drainage in that area, as that appears to be the side of your cactus where the problem is beginning. Or perhaps there is an issue with your drip irrigation system.

Remove the stone mulch and have a little dig to check soil conditions.

Dan

to post multiple pictures you will need to use a hosting site. many of us use photobucket it's free. once uploaded to the site, simply copy past the HTML code into your post. It will look strange, but when you look at the preview , if you did it right, your pictures will show there