That would be some kind of scale. Yes you can scrape them off. Treating with dormant oil and possibly an insecticide would be easier. You may be past dormant oil spray time but could still apply an all season oil.

Thanks a lot! Have removed all of them.

One question if I may: these things had no visible means of locomotion. No legs or wings I could see, in fact did not even seem to have a defensive reflex when flicked off onto the plate. How do they move? Specifically how did they get all clustered up on a branch 4-7ft off the ground, without any evidence of them anywhere else on the tree (or elsewhere in the garden that I could find -- checked all the fruit trees). Certainly did not have wings. Could I create a barrier on the trunk and prevent them from ever crawling up? Or do they hitch a ride with flying insects or birds or some such.

apologies for the last question -- looked up their life cycle and have a better understanding now. Hopefully can avoid any further problems. Thx again for the quick ID.