Q.Dwarf Imperial Mandarine
It is about 3 years that I have planted the tree.Every year I get full of little fruits . About the size of pepper seeds but after sometime they fall off. I have tried many things.Like potash and sodium sulfate.Nothing seems to be helping.Some leaves have specks of yellow.Only thing is it is planted in semi shade.What can I do about it? Can you please advice me.
The problem of fruits falling off may get better as the tree gets more mature. Young plants may drop fruit because they're not able to handle the load yet. Please see the following articles:
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-fruit-drop.htm
http://www.harlowgardens.com/citrus-fruit-and-blossom-drop/
Also check the leaves for pests. For example, mites can create small yellow specks on citrus leaves when they feed:
http://ipm.ucanr.edu/PMG/r107400111.html
There might also be a pollination problem. This article is about limes, but the advice applies to other citrus trees:
https://www.gardeningknowhow.com/edible/fruits/lime/hand-pollinating-limes.htm