I pruned my 7 year old Crepe Myrtle late spring this year (in Central Florida). It it usually has good growth by this time, no blooms as it is a late bloomer. But this year it isn't sprouting normal shoots but small tight patches of growth, almost like lichen, the only shoots are at the bottom. Did I kill it when I pruned it?
Crepe Myrtle – Weird Growth
If the tree is putting up new shoots from the ground, it isn't dead., I don't know what the weird growth would be. If that continues, you may need to remove the limbs on which it is located. I would suggest taking a sample to your local agricultural extension office for identification and recommendations.