I’ve had some kind of illness with tomato plants and it spread in a way that is pathogenic where a 3rd plant was kept separate but upon leaving in closer proximity it become infected. I thought the first two were due to some circumstantial factors like using some soil from another plant that died, or pots with poor drainage, but the third plant did not have these factors. So am I forced to clean surfaces, toss the soil and start over, or can I reclaim the soil?
You can leave soil out on a tarp in the sun but as Gunther says you don’t want to sterilise it completely. It’s the bacteria that break down the organic matter into nutrients the plants can absorb.
If you’re worried about the blight returning and don’t want to replace the soil I’d think about switching crop for next year. Maybe some nitrogen fixing beans instead?