Another sign to have noted is if the tree carried a normal blossom load but the set fruitlets fell in June. This is what we call in UK, June drop which is usually weather induced. The trees however do retain a small number of fruits which will mature correctly. A 15 years old tree could have cropped well even heavily until this year and now needs to regain it's strength. There are other issues which could together create the loss of cropping. Do you feed the tree?Interesting, thanks. In 15 years, we never had a problem. Let's see what happens next year.