Thanks for your answers.
I've tossed a lot of potted plants, so it is a lot of dirt - and in any event, I'm not sure how you would "pasteurize" soil.... heat up wet soil in the oven or microwave? DH would probably take a dim view of that, even if I didn't. I guess I will keep the dirt in the black plastic bags (where it currently is) and wait for summer to bake it.
The rust may have come in from some new plant or other, and spread from there. The first and last time the garden was this badly hit was in 2006, and I went through a rust purge then, getting rid of most of the susceptible plants. (I did keep a few for one reason or another; oddly enough, I have not seen rust on those plants since then. They are in a different part of the property than the current problem area.) Although we don't get cold winters here, thankfully the weather is usually not conducive to rust.
I am trying to look on the sunny side of this current infestation... it forces me to get rid of some plants (I have way too many for our shady property, anyway, which is why the pots), it forces me to take a hard look at what is left (is this plant going to cause me hassle in the future?) and it has forced me to re-think my pollen dabbing schemes somewhat (hopefully to the benefit (rust resistance) of future seedlings).
