There are a few thing you can try to protect your apples:

1. Bag the fruit to prevent the female insects from laying their eggs. You need to snip the corners off of the bags to let air into the fruit.

2. You can try coating the fruits in kaolin clay powder which is supposed to prevent the adult flies recognizing the fruit as a host. This should be applied before the flies become active and will need reapplied every week or so.

3. Hang yellow sticky traps in the trees to trap the flies or special spherical red traps - make your own by hanging wooden or rubber balls painted red and covered in a sticky substance (Vaseline?)

5. Make sure you clean up around the trees as soon as possible when fruit and leaves drop to the ground - this will reduce the number of larvae that make it into the soil to pupate and survive the winter

Apple maggot worms can be difficult to control and require persistence. I hope this gives you a few ideas to try next year