Borers feed throughout the winter and spring, so if you think your trees are currently infested, you can try to kill individual borers by inserting a flexible wire into their holes. There are no pests evident. Mother Nature's way of thinning. This is normal for a tree that is loaded with fruit. Often it is a lack of pollination or some other damage to the seed or embryo.
Every product has a pre-harvest interval.
Once this time has passed the fruit is totally safe to eat. Check the label of the product to see how long this period is. Generally speaking, most insecticides last only 3 to 5 days at the most. 5. Yes, but it will not come back exactly as the same cultivar. However, if you wish to try, they will either need to be stratified artificially or by Mother Nature.