there are several causes of fruit drop.
1. At this time of year plants shed excess fruit due to a hormonal thing. it means the plant hangs onto fewer fruit but they get bigger. its called 'June drop' but lasts into July. There is nothing you can do about it I'm afraid.
2. Has your area been particularly dry as lack of water can also cause fruit drop as the tree tries to survive. Obviously lots of watering can be done.