Yep, it's best to tear them out and put in new plants. Here in the Dallas area the time to put out new plants is now or last week.
http://forums.gardenweb.com/forums/load/tomato/msg072240396231.html?1

Pete

If they are indeterminate, I would think that plants with a much larger root system would produce better but I've never grown tomatoes in Texas. If it were me, I would try cutting them back(indeterminates) and feeding them just a little nitrogen until temps got low enough to start producing again. Then give them what they need to start fruiting.
They have slowed a bit but never really stopped for me, here or in CA. But I do spank my plants when not setting fruit.
If determinates them I would definitely plant new plants.

Another thought, if you decide to cut them back always cut above a node(where a leaf and/or sucker was/is).
Maybe try this with an extra plant if you have the room to spare?
I'm sure someone else who has grown in your situation (TX or similar) will chime in if I'm dead wrong/right. LOL!

Thanks for the replies. I think I'll tear most out, but will leave one or two as an experiment.

S

Have you thought about taking one of the healthy branches and potting it up? Tomatoes grow roots from the stem/branch area so you could "start" a new plant from the old one.

Agreed. Probably the easiest way to get new plants is too root a sucker then tear out the old plants. Never actually done it myself from beginning to end; since my season is much shorter than yours, but I have rooted a sucker just to try it out and it's fairly easy and from what I've read the resulting plants grow vigorously.

Heck you could just put a sucker close to the ground while it's still attached to the mother plant and cover part of it with dirt. Wait a week or two until it develops it's own root system and sever it from the mother plant. Then remove the original plant.

There are lots of variations of this same principal; since tomato stems put out roots so readily.

Gardenvt and Jeremyjs,

Rooting a branch / sucker is the coolest idea! Thanks so much. It sure beats buying a bunch of new plants. I have never rooted a tomato plant, but I will give this a try.

Shane

I kept a producing cherry plant from spring of 2014. Water and food. It's still alive. I now have 7 from spring plant I'm experimenting on.they all have new growth. It's fun.