Codling moth larvae eat into the core from the blossom end or through the side of the apple. The larvae overwinter under bark, in or around packing sheds, and in the soil.
Adults begin to emerge about the time the last petals fall from the apple blossoms.
The eggs are laid at night on leaves and twigs a short distance from a cluster of apples. The larvae feed slightly on leaves but soon crawl to the apples and chew their way into the fruit. Some of the infested apples drop from the tree. There are two generations each year in Iowa.