It had some leaves but the top of the branches did not. Then one day no leaves. It had ants on it last year. I have only had it a year.
Crepe Myrtle Has No Leaves
Certified GKH Gardening Expert
If you found ants on the tree is can be a sign of honeydew. It is secreted by insects and it attracts the ants.
You can treat the Crepe Myrtle with Neem Oil.
Here is links with more information and will refresh you on the care needed.