Where does the blight come from? Are potato farmers' fields full of blight? Seems like they wouldn't last very long as potato farmers if that were the case.
Blight or Late blight - https://en.wikipedia.org/wiki/Phytophthora_infestans
Early Blight - https://en.wikipedia.org/wiki/Alternaria_solani
Both need moist environments and the former, water-saturated or nearly saturated environments and the latter, humidity and wet leaves.
Air conditioned grocery stores and homes are dry so I can't see those places being loaded with blight spores.
There seems to be a 50/50 split in people that say store bought potatoes are fine to plant and people saying you shouldn't plant them. Some people say they are sprayed with something to keep them from sprouting but all the ones I've bought will sprout.
I've always bought seed potatoes from the grocery store. Since grocery stores are a place you can purchase seed potatoes, that kind of rules out it being a source for blight. My little grocery store keeps the seed potatoes 10 foot away from the eating potatoes. Seems like they'd come in the same trucks too because I doubt there are special trucks delivering seed potatoes out here in the boonies.
Reading the two wiki pages, it seems like the spores have a hard time living when conditions aren't ideal, mostly in the wet soil or on the wet foliage or tubers in the soil or culls piled up on the soil. The spores can travel with the wind for a time. Dry and/or warm conditions will kill them, however one of them can stay with the tuber and make it rot later. Which all brings me back to potato farmers' fields being loaded with blight in which case, they'd not be farmers for very long.
Reading up on them makes me think about something else. They say to dig taters when the soil is dry but one year I pulled plants up taters and all while the soil was moist and that was a lot easier than digging heavy, dry soil. Maybe they say to dig dry to prevent you from bringing blight into your root cellar which is cool and moist, ideal conditions for blight to survive.
https://freerepublic.com/focus/f-chat/4048051/posts?page=119#119
Later the potatoes have soil ridged over the rows ("hilled") to prevent greening and control weeds in the row.
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The plastic mulch also prevents weeds and eliminates the need to hill and cultivate.
https://extension.psu.edu/potato-production
So it's mostly about covering any tubers that may end up sticking out of the soil to prevent greening and also helps with weeds. Using plastic mulch does the same as hilling. I'm thinking I need some plastic mulch because I decided to feed hay to the goats down in my bigger garden area where I grow potatoes. I did it for two reasons.
1) my little bitty tractor can't lift a round bale of hay but can pull a pallet with a round bale on it, barely. That area was easy to get to.
2) Last place I fed hay, when I forked the hay off, it was a good mixture of manure/pee/hay for composting and the soil underneath was black, moist and fluffy and had the biggest worms I've seen here.
I'm sure it also dumps a bunch of grass seed as well though so weeding will be nearly impossible to keep up with this year. There's a property down the road that had a bunch of blue barrels get strewn around during a storm 4-5 years ago and they've left them just sitting in the woods since. Gonna stop by and ask if I can have them. Maybe I'll just do container taters this year. 10-15 open bottomed half sections ought to grow quite a bit.
I lay the potatoes directly on the ground inside the bucket, add some bone meal, and then cover the seed potatoes with wood chips. As the plants grow, I add more wood chips.
Don't know any place to get wood chips. I've heard of people using straw though and I can get that but have to travel quite a ways.
What I am saying is, don’t save your table potatoes that have sprouted. Don’t plant them. They are a nightshade.
Cerified seed potatoes are seed that has been certified for purity and freedom from disease by the Dept of Agriculture. They are clones.
Some more blight info: https://blogs.cornell.edu/livegpath/gallery/tomato/tomato-late-blight/