But with careful selection and some diligent care, apples can be grown as low or no-spray crops. All trees now sold commercially are grafts. The top portion is the variety you have chosen. It is the part that bears the fruit and requires your attention as a grower. For instance M.9 will produce a strongly dwarfed tree of about 8 - 10 feet, but is susceptible to fire blight.
Rootstocks are crucial to the health of the tree, but have no affect on the fruit.
Another major consideration with apple growing is pollination. Few apple varieties are self-pollinating. Some are even sterile. In general, all apple varieties should be considered self incompatible and at least two varieties should be grown. Additionally, you'll need to make sure those varieties are in bloom at the same time.