Q: Can you tell me what is wrong with this crepe myrtle? It is losing its branches.
A: One of the results of chopping off the top of a crapemyrtle in winter is lots of lush growth the following spring. The stems thus produced are weakly attached. A rain storm results in many twigs falling to the ground.
Consider changing your pruning habits to leave more of a “brushy top”, with many small branches coming from multiple places at the top of the crapemyrtle trunks, instead of shortening them all to a central spot.