Sounds to me like powdery mildew, keep well watered in future during long dry spells and if you like you could spray with a fungicide, in the past i have dealt wth this by cutting back the worse infected growth and kept well watered to good effect, euonymous is very tough so dont be too worried.

Thanks Julien - the only problem with cutting back is the fact it is all the lower stems that are affected down to the soil, the green is all at the top of the shrub.

Could be Euonymus scale - the male scales are covered in white, so it looks like mildew. Needs treating - google Euonymus scale for info, the treatment used to be malathion, but that's been withdrawn, so maybe Provado make something for it. But google first to check whether it's that and not - no point spraying if the nymphs aren't hatched out, which usually happens early summer and if there's a second lot, around now through to early autumn.

Thanks all will do as you suggest.