It is normal for fruit trees to drop some of their fruit in June. They get rid of the fruit that they can't bring to maturity. If a tree drops most of it's fruit then it is usually because of weather conditions, not enough water and the roots become too dry plus soil that is either too acid or too alkaline for the tree. Also it might have had a lot of fruit last year and so will skip this year. If fruit trees crop too heavily, they then become bi-annual bearers .Next spring make sure you water the tree well before it flowers and scatter fertilizer all around the drip line of the tree.