In addition to spraying, prune the apple trees.
Here is an example of a home fruit tree spray. This spray at petal fall is the most important one of the year. It will do the most for keeping pests under control and making sure you have an edible apple crop. SPRAY #3: Two weeks after Spray #2, you will spray the same Home Fruit Tree Spray again (the spray not the oil).
This every two week regiment will prevent bugs from getting into your apples as. The main objective in spraying apple trees is to prevent insect damage to the fruit. The most important period to spray apple trees is from petal drop until just prior to harvest. Several applications will need to be made during this period.
A home orchard type spray (available at most garden centers) is the best product for home gardeners. Most home orchard type sprays contain 2 insecticides and 1 fungicide. Spray the apple tree with horticultural oil while dormant, then again when the leaves are 1/2 inch and again right before the tree blooms, when the small buds begin to turn pink. Apple maggot control begins before the tree produces foliage in the spring with a lime-sulfur spray. To control the many other insects that attack apple trees, use an insecticide when the blossoms start to drop and then three more times.