Hi Ken,

Apple maggots and plum curculio are two pests that do this to your fruit. You either need to use regular chemical sprays to protect your apples or you need to physically protect the fruit so the bugs can't reach them.

This page has details on both chemical and organic methods to get good apples:

https://extension.umn.edu/yard-and-garden-insects/apple-maggot

If you choose to bag, do so when the apples are grape-sized. Here's how it works

1. Cut the bottom corners of the baggies off. This will allow moisture and rain water to drain.

2. Look for apples that have no scars or marks. If two or three apples are growing in a cluster, choose the best one and pull off the others.

3. Open a baggie, and slip the apple inside, taking care to keep leaves out of the bag. Press the seal on the bag closed from either side of the apple.

4. To make sure the baggie doesn't fly off the tree over the summer, secure it by stapling the closed bag at the top on either side of the fruit stem.

Hope this helps. Good luck!