would it contaminate my plot. I missed the boat in digging them up at the right time, and now most of them are half rotten. Not sure I can face digging up all those rotting spuds this weekend.
So, what if I just left them to rot over winter? What's the worst that could happen? And is this likely? Might they just rot away and I can start all iver again planting something else in that area next year?
If they were blighted then you should really get rid of them
https://www.rhs.org.uk/advice/profile?pid=217 - "•Destroy all potatoes left in the soil and waste from storage before the following spring"
I'm not sure if they had blight or not, really
If the foliage rotted during warm weather then it's almost certainly blight. Use what you ca, and be ruthless about destroying any that come up next year. Don't treat them as a free crop.
I can leave mine in the ground during winter and only harvest as required (a cheap root cellar for me), as long as I dig the remainder before any warmth in the soil starts which promotes shooting again. In fact for some unknown reason (could be the hot dry weather I am experiencing) I still have a few dormant ones in the garden which I will be digging later today. At the same time my new crop is just starting to flower.
Blight can only survive on living plants - that's why - in our climate - potatoes are so much more dangerous than tomatoes (provided the whole tomato plant is exposed to frost and nothing is left alive).
So the potatoes that rot away completely are no risk - but bits that are still rotting in spring might be a problem if you expose them while they have some life - I don't know for sure but I'd be very careful.
What's certain is that any shoots/volunteers coming up from infected potatoes (or peelings) are the primary cause of next year's blight.
Best to dig them up before spring and destroy them - though any tubers that look really good can be eaten (careful with the peelings). Blight hasn't poisoned anyone yet though it has starved millions to death - also it tastes so awful you'll be in no doubt if it is tainted (best to taste before mashing!).
Cheers.