Guy Ames has a new website, runs a small nursery in Arkansas specializing in varieties proven disease resistant in his orchard. Not just the usual suspects, e.g. Porter’s Perfection, an English bittersweet cider apple, growing happily in Arkansas.
These all thrived with no irrigation, spray or pruning for ten years: Arkansas Black, Enterprise, Capt. Davis, King David, Shannon, Black Limbertwig, Arkansaw, Tull, Porters Perfection, Williams Pride, Stayman Winesap, and Royal Limbertwig.
He writes most of the variety descriptions from scratch and from firsthand observation. Don’t know if he ships, maybe not, but his work tracking disease traits can likely save you heartache and time if you’re a Southern grower in conditions similar to Guy’s.
And yes diseases do vary from place to place, soil to soil, etc. But still I would start here (and with Scott Smith’s bulletproof Top
Ten list) when planning an orchard in the South, especially a no-spray orchard.