Apple leave and fruit drop
My apple tree blooms, (I have never sprayed or treated the trees with any pesticides.). Then the leaves get a brown spot and fall off followed by the apples dropping. This has happened for the last 2 years. I would say around late June/July, before apples are ripe. By harvest the tree is bare. It is a red delicious variety of apples. I have read that it could be a fungus.
Queen Anne's County Maryland
In general apples are susceptible to several insect and disease issues such as scab, rust, fungal leaf spots, etc. You will have to familiarize yourself with these problems. See our website below. Based on your description it sounds like it may be scab as you mentioned defoliation and early fruit drop. https://extension.umd.edu/hgic/topics/apple-pear-diseases
Another reason for fruit drop is that the tree may need a pollenizer tree. Apples are generally self-unfruitful and require pollen from another variety within 100 feet to produce a good crop. See more https://extension.umd.edu/hgic/topics/tree-fruit-pollination
In general, apple trees eventually require a spray schedule for control. See our website for care, problems, when to spray fruit trees, and the Va Tech Spray Schedule. https://extension.umd.edu/hgic/topics/apples-selection-and-planting
If you notice problems this season, please send us photos so we can see what you may be dealing with.