great fruit trees

Question

FRUIT GETS ABOUT THE SIZE OF A GOLF BALL THEN FALLS OFF TREE. WHAT WOULD CAUSE THIS PROBLEM?

Answer 1

Sudden drops in temperatures, rain or watering fluctuations, disease, pests, nutrient issues and poor pollination are all reasons for bud or fruit dropping.
Some fruit selectively drops also.

This article addresses the issue, in Lemon Trees though the issue is the same.

https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-fruit-drop.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/grapefruit-tree-not-producing.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/hand-pollinating-grapefruits.htm
https://www.gardeningknowhow.com/edible/fruits/grapefruit/growing-grapefruit.htm