Cereus Peruvianus Disease?

[cactusce]

I have had this cactus for the last year or so. It seemed to be doing just fine, but recently I noticed these white spots at the top of the larger. I have had issues with scale and mealy bugs in the past, but I didn't think this was a result of either.

Is this some sort of fungal disease? Will it spread down the stem? Do I need to perform some surgery?

I actually had another Peruvianus that started to rot and turn brown at the top. I cut the top off, and there is already some nice growth coming back.

http://i.imgur.com/VLWk6Hx.jpg
http://i.imgur.com/jYyzCom.jpg
http://i.imgur.com/gDAon5O.jpg

[hegar]

I will go out on a limb and state, that those splotches are some kind of fungal disease. I would cut the stem pieces off that are infected and discard them. Most likely, you do have a plant fungus that does not cause a rot of the stem, but stays mostly near the surface. However, these fungal spots produce fruit structures, which will release spores and via water splashing or air movement result in the formation of additional lesions. So I would advise you to not wait much longer and start the necessary treatment to save your plant. Please keep in mind though, that whenever you cut near a lesion, make sure, that you disinfect the knife at least prior to the last cut you make into healthy plant tissue.
You can use isopropyl alcohol (rubbing alcohol) or a bleach solution for disinfecting your cutting tool.

Harald