how do you get flies off an Empress tree

Question

Last year our Empress tree was covered in flies eating away at the leaves.

Answer 1

I have a hunch your empress tree was covered in whiteflies. For more information on whiteflies and a course of treatment, please visit the following link:
https://www.gardeningknowhow.com/plant-problems/pests/insects/whitefly-control.htm

For more information on the care of empress trees, please visit the following link:
https://www.gardeningknowhow.com/ornamental/trees/royal-empress/worlds-fastest-growing-shade-tree.htm

Answer 2

use a systemic insecticide like bayer. apply to the ground under the tree's drip edge. water it in heavily.