I have had Spitz growing here for quite a while and have gotten few apples. First I lost it to blight, then I had it in a spot with too little sun.
@Ruben, for the peaches and plums I wrote up another report,
Overall I would say the biggest disease problem with apples are rots, half of all varieties rot too much in the mid-Atlantic. Pears also can have rot problems but they are overall easier. For peaches and plums brown rot is the main problem so you need varieties resistant to that. My favorites are all pretty resistant as I suffered with a lot of rot and removed any variety that was a problem.