As soon as flower petals have all fallen, it is time to protect apples, and to a lesser extent pears, from codling moths. Codling moths lay their eggs on developing fruit. Eggs hatch into worms which bore into the fruit. Insecticides such as malathion and carbaryl (Sevin) kill the worms as they hatch. They need to be applied every two weeks until about August first.
Codling moth traps can be placed in trees to trap the male moths. They are attracted to the pheromone in the traps. If enough traps are placed in trees, virtually all the male moths are trapped. Without fertilization, the female moths lay infertile eggs. Large trees may need up to 5 traps. Three traps is normal for most semi-dwarf trees. If you have some large neighboring trees which do not have traps, your traps may not be completely effective.