I recently grafted two apple trees, a Somerset and a Pink Lady. I cannot recall, but I believe they were done on the correct M rootstock. I grafted them in Blacksburg, VA, but live in Richmond where it is much hotter and more humid. Anyway, they are both a bit over a foot tall and the new growth from the scions has started to wilt, even though they are fully-watered. Is it just too hot here for these cultivars?
If the heat is the problem it's probably due to them being fresh grafts rather than what kinds of apple trees they are. 'Pink Lady', for instance originated in southern Australia. Try shading them until they are older.
Also, the Pink Lady has growth coming from both the rootstock and scion. Should I prune the branches coming from the rootstock?
