I'm can't figure out what it is, but I don't see galls unless you're thinking of the distorted growth at the nodes? Galls aren't necessarily caused by aphids, could be gall midges, sawflies, mites etc. I looked at some pics on Google for willow galls and didn't see any that looked similar. Cutting back is certainly an option, and destroy the trimmings if you can. If it comes back next year maybe you can post some more pics?
