The method used by most gardeners to control these bad guys is dormant spraying. One really great thing about dormant sprays is that many of the most effective materials you can apply are of natural origin. Natural dormant spray materials are commonly sold at most garden centers and nurseries. I am also a rather big believer in the use of paraffin oils instead of the more common petroleum based dormant oils. Dormant spraying of your fruit trees is probably as important to the overall well being and productivity as proper pruning and feeding.
Timing is easy, just wait until the tree goes dormant.
I like to apply two applications of different dormant sprays before pruning, one after pruning and then dormant oil to seal in and suffocate the bad guys as well as seal out other unwanted visitors. My favorite spray program includes a couple of applications of a homemade spray, an application of Copper sulfate after pruning, and then I apply dormant oil. After mixing this material into my sprayer I find that if I shake this mixture vigorously it seems to blend up very well. I often agitate this material during application as well to ensure continued mixing. This exposes pests to the elements and often causes them to lose body fluids, thus eliminating them.