Cherry tree…no fruit and leaves

Question

The leaves have a black substance like eggs and a lot of ants on the tree.

Answer 1

The black substance is sooty mold which is a type of mold that grows in the honeydew secreted by aphids. Wherever you have aphids you typically have ants because ants and aphids have a mutually beneficial relationship. Ants protect aphids in return for honeydew.

Here are some articles on sooty mold and aphids that will provide you with more information, including a course of treatment:

https://www.gardeningknowhow.com/plant-problems/disease/how-to-get-rid-of-sooty-mold.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/controlling-aphids-and-ants.htm
https://www.gardeningknowhow.com/plant-problems/pests/insects/homemade-aphid-control.htm