On Page 3 we discussed planting apple trees. But novices also need to know about pruning apple trees, once they get them in the ground. In pruning to try to give them an optimal shape and structure, you're essentially focusing on the leader and on establishing good scaffold branches. A prime objective in pruning apple trees is to ensure good aeration. I.e., if air circulates freely through all the branches, there's less chance of a problem with powdery mildew disease. Pruning also restricts the vertical growth of the apple trees, making it easy for you to get at them in your attempts to provide adequate apple tree care.
In addition to pruning, the branches are trained -- in a process called, "spreading" (illustrated in Marie Iannotti's tutorial on pruning apple trees) -- to form angles that will help them radiate out from the trunk, while maintaining sufficient strength to bear heavy loads. And speaking of loads, believe it or not, there can be such a thing as thing as "too many apples." While you're waiting for your young tree to produce any fruit at all, this can seem like an enviable problem to have. But a problem it is, and it's dealt with through a process known as "thinning."
Thinning promotes larger fruit size, improves next year's blooming and reduces the likelihood of limbs snapping off. Thinning works on two levels: the blossom level and the branch level. Apple blossoms form a cluster, consisting of five or six potential fruits. You'll want to thin these down to one fruit, once the baby apples have reached about the size of a marble. At the branch level, remove enough fruit so that the remaining apples are spaced about 4"-6" apart.
Even if you have disease-resistant varieties, you still have to worry about insect pests. To combat scales, mites and aphids, spray a horticultural oil on apple trees just after full bloom is over, and thereafter spray every 10-14 days throughout the summer. For apple maggots, codling moths, green fruitworms and plum curculios, check with your local county extension office for the best pesticide to apply in your area. Some apple tree growers are experimenting with neem oil as an organic alternative for curculio control.
Voles or "meadow mice" are the next greatest menace to apple trees, after disease and insects. Please consult my full treatment of vole control for tips on how to identify and control these pesky nibblers.