Why are mulberry trees dropping premature fruits?
Why Are Mulberry Trees Dropping Premature Fruits
Many fruit trees drop both immature and almost mature fruit for several reasons. Sometimes, it is because there are too many fruit for the tree to grow to maturity. The following article is geared toward figs, but the information would be the same for mulberries or most any other fruit: https://www.gardeningknowhow.com/edible/fruits/figs/fig-drop.htm