Oren wrote in
:

On Fri, 21 Dec 2012 12:12:24 -0800 (PST), scott
wrote:

Wondering what this is and what (if anything) I need to do? Anything
to worry about? Location: backyard patio, desert landscaping, Las
Vegas area. Thank you.

Picture of spot-- http://imgur.com/aw252

Efflorescence.


Yup.


Do you have a water pipe leak under the concrete?


In this case, possibly due to watering plants near the patio.

The concrete in the photo is breaking up, so this has been going on for
quite a while. Redirect the water, improve the drainage, or find a way to
seal the underside of the concrete from water ingress


--
Tegger