Do you mean insects? It would be helpful if you could upload a photo, do you know what sort of euonymus it is, is it evergreen ? :-)

Sounds like Euonymus scale - the newly hatched nymphs are present only in early summer and early autumn, and this is the time to spray to kill them off - adults are difficult to treat for. Treatment used to be malathion, but I know that's been withdrawn - you had better check the pesticide range at the garden centre for something that treats it, probably Provado has something available in their range.

Thankyou. It is an evergreen, we have lived here for 14 years and it was already well established when we arrived. The white things may be alive but I can't see any moving around - they look like white vermicelli. The leaves get a bronzish hue before falling. My son is charging his camera so we can send a photo.

You don't need to, it is, without a doubt, Euonymus scale, particularly now you've confirmed its evergreen - the nymphs are either newly laid or about to hatch so get ready to treat end of August or September.