My onions got white rot just before I went abroad for 3 weeks, no time to grub them out and destroy. Hideous sight, yellow blotchy/grey foliage drooping everywhere. Got back 2 days ago and to my surprise they are growing through it, greening up, and the bulbs, though small, are firm where they were slimy. I'm trying to use them up fast, and cutting the bad bits off as suggested above.
Good tip about freezing them after frying, thanks.