When winter approaches, insects that ravish fruit trees (such as red spider mites and aphids) lay their eggs on the trunk before freezing to death, thereby ensuring another generation of pests. Unless, that is, you take action. In early spring, about a week before the tree starts budding, spray it with a diluted dormant oil spray (which is a highly refined petroleum oil) that suffocates the larvae. And, because of how it works, it's impossible for pests to become immune to it. When you apply it, make sure to cover the whole tree in order to create an impenetrable choking layer.