Anybody????

Have you evaluated all of the possible environmental and cultural factors carefully? Lack of nitrogen (at the right time), insufficient pollination, cold injury, lack of rainfall, and other factors can effect ability for a fruit tree to hold its fruit. Age might be a factor, too.

Even though peaches are self-fruitful, pollination can be affected negatively by the weather, lack of bees, overhead irrigation, etc.

Take a look at this PDF file on reasons for fruit drop and see if anything rings a bell. The first half of the article deals with factors relating to fruit drop...while the other half discusses why it is so important and how orchardists can facilitate fruit drop more efficiently. (That's not the part of interest to you, obviously!)

Here is a link that might be useful: click here

I would say it's was unfertilized fruit.