Hard to tell from that pic, but my guess is aphids. (I'm basing this on the 'little green bug' description). If so, you could spray with neem.
Search around for photos of aphids and see if they look similar to you. Then search for solutions for aphids (if it's them)... you'll find plenty.
IMO, it doesn't sound so much like mites, though I could be wrong. I personally haven't seen green ones, and am used to seeing mites on the underside of leaves, rather than on stems.