Remove them which they begin to interfere with the permanent branches. This encourages the tree to spread, permitting more sunlight to reach the interior. The central leader will continue to grow upright and produce laterals if not pruned. Trees trained to the central leader system develop wide angle branches and are less subject to limb breaking. Trees are cone shaped and are best suited to close spacing.
Fruit is produced higher from the ground, necessitating the use of ladders.
Little pruning is necessary after the primary scaffolds and modified leader have been developed. Keep all scaffold branches growing about the same rate. An over-vigorous branch tends to shade others and may eventually compete with the leader. Keep all suckers and water sprouts removed. Further pruning is seldom necessary until the tree begins to bear.