Every now and then my crepe myrtles leaves go funny. I thought it was aphids and iron deficiency but I've given iron and usually you can find some aphids on the plant when they cause this and I can't see any.
Hi Beano, This looks like a bad infestation of scale to me. Not absolutely sure but it does look like White scale, something that I have had on one of my figs. I wiped the leaves with a soft cloth and some white oil to get rid of them and then use a systemic insecticide to stop them coming back. If you can get to the Bimer show next weekend, bring a couple of leaves in and lets have a look. Michael.