What is This?

I saw this a couple of weeks ago and thought it was the outer skin of plant developing bumps............looked closer today and started plucking these things off that were clinging to stem.......most were hollow with white chalky powder on stem....some had a little fluid come out of it....., but nothing was alive or moving.....
Can anyone tell me what this might be?.....It appears to be slowly killing the stems that it was on........

Scale.

Scales. They suck. Sap plant juices. Kill em.

Rub diatomacious earth all over the branches

a video(movie) of all pests in a marijuana garden would be awesome that way you could see them in action. 2 buddys smoke this new strain that shrinks them(like honey I shrunk the kids) and they go out battling the pests up close and personal. lol I would buy it. sometimes pictures don't do it justice

The devil ...