All the above guys gave good advice. March is a good time to prune before the trees start to come out of dormancy. That's when I prune mine & it's past the worst of the cold. I usually fertilize the camp's trees in early April, and spread some 15-15-15 or 19-19-19 under the edges of the landscape cloth around the trees.
At this time of the year, Japanese beetles seem to be the biggest threat. Sevin or Bonide fruit tree spray work to keep them off the trees. Some of our trees look like yours with the bug damage, but no worries.
Spend some time researching how to prune apple trees and train the limbs. Getting the shape of the tree right can save on disease problems and broken limbs from heavy fruit loads. Shaping the trees to a central leader also gets more sunlight to all parts of the tree from the top down. Think " Christmas tree " for a shape with the longest limbs at the bottom and the shortest ones at the top. Limb angles should be 90 degrees to the trunk ( straight out ) to 60 degrees upward. 60 degrees is about perfect from all I've read. Check into U. of Wisconsin for apple tree info on pruning and care, or U. of Minn., Penn State, or Cornell. Much good info to be had at those places.