meyer lemon trees

Question

what causes the fruit when tree is young to turn yellow and drop off

Answer 1

These articles will help you.

https://www.gardeningknowhow.com/edible/fruits/lemons/growing-meyer-lemons.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-fruit-drop.htm
https://www.gardeningknowhow.com/edible/fruits/lime/is-lime-fruit-and-lime-blossoms-falling-off-tree-normal.htm