It is difficult to tell because the sun is so bright on the tree, but the trunk looks like it has a bad case of scale-in which case you need to spray. But an oil spray would likely cause burn in the summer heat. I would ask a reputable Nurseryman for an opinion before doing anything. I love crepe myrtles. When we lived in Louisiana they were everywhere.
OOOoooh! That's a HORRIBLE scale attack- I doubt that any water would take care of that. After spraying with whatever your nursery person suggests, I would definitely get some systemic insecticide to work in around the roots for the future. Ask for suggestions for that too. It's the same systemic used for roses- don't use it near food!!! Possibly you could even use a long handled brush with dishwashing liquid and water and scrub a lot of the scale off. It looks like the trunks are fairly exposed- that will help get the varmints off! I shiver just looking at the photo! Incredible that you didn't notice the problem before now.
ecrane3, After blasting with the hose, I would spray with insecticidal soap & treat with a systemic. If the heat is still on during the day, you could spray in the evening, then hose it off the next morning. I know that's alot of work, but I've never seen such a heavy infestation, and it could kill the plant. In any event, it's going to take more than one treatment.
I have a couple of citrus that get all kinds of scale and mealiebugs. I have tried the Bayer product, but it works very slowly, and I don't want to kill Honeybees in the process, so this year I have started alternating between light oil spray (to suffocate) and Insecticidal soap (the fatty acids eat through the waxy couting, in theory) on a two week schedule in spring. Summer gets to be a problem because of the heat and the proximity of the neighbors.
Thank you all for the advice and info!!! I just now got back here to see the replies ya'll sent. I haven't yet gone to the A&M web site, am about to... but I am freaking out that this is an insect!!! My poor little tree!!!! No wonder he hasn't felt like blooming big and pretty like last year!!!