Our crepe myrtle (at least 15 years old) grew many little spikes on the trunk over the past month or so. They look like 4-inch-long pieces of angel hair pasta, sticking out all over the main trunk. Now, the branches are dying in chunks. Any idea what the problem might be? I'm not finding a match with typical myrtle tree diseases/issues.
Crape Myrtle Issue
Certified GKH Gardening Expert
From your description is sounds like spindle galls, which are caused by an infestation of pests; it could be any number of pests.
Do further inspection of the tree and look for any other signs of pest or disease.
These links will help you pinpoint the issue.