Is this blight or something else?
 

My tomatoe vines are turning brown/black while the plants are still green and some have fruit. Can someone identify what this is and if it's treatable or are the plants doomed? I've attached photos of the problem. Any advice or help ia greatly appreciated.

Oy. The photo is a bit blurred, but that looks like it might be gray mold. I hope I'm wrong.

Timber rot or southern stem blight possibly.will await the opinions of the more southern experts.
KarenO

[SIZE=2]Alternaria stem canker is what I think it is because of the concentric rings.
[/SIZE]

I would say you nailed it PATIHUM
KarenO

Ditto, nailed it Patihum! :D
We get grey mold (Botrytis) here and some Alternaria (early blight) - and on the stems, grey mold is worse in my experience. the Alternaria stem lesions, with the concentric rings, tend to be shallower and the plants can survive for quite some time - even months if not badly affected. The grey mold on stems will usually eat through and kill the stem within a week. That is in a greenhouse environment where the plants are protected from rain but get high humidity.

I didn't know what that was. I looked up a site [URL]http://tomatodiseasehelp.com/alternaria-cankers[/URL]

Here's a picture on the stem:
[URL]http://aggie-horticulture.tamu.edu/vegetable/problem-solvers/tomato-problem-solver/stems/alternaria-canker/[/URL]
They say it will kill the plant when it girdles the stem. :(
Some varieties are resistant, maybe that's why they didn't kill the ones I saw it on. :?!?: I guess in different conditions they may grow and spread fast.