The maggot leaves through a small opening made in the side of the fruit and enters the soil. Maggots usually settle in the top 1 to 3 inches of soil. The maggot transforms into a brown, hard, oval puparium within which the true pupa is formed. Some of the first brood pupae transform to adults and emerge in late August and September. However, the majority remain in the soil through two winters before appearing as adult flies.
Few maggots leave the fruits while they are still hanging on the trees.
Usually a few days elapse between the time an apple maggot-infested apple falls to the ground and the maggots leave it. Dropped fruits of early varieties should be collected two to three times a week and those of later varieties at least once a week. Collected fruits should be put in a tightly sealed plastic bag and placed in a garbage can. In addition, the removal of hawthorn or other alternate hosts in the vicinity is a good practice. As mentioned, maggots leave the fruit that has fallen to the ground, burrow into the soil and change to the pupa stage.