From the images sent outside of this system, these appear to be woolly aphids. Wooly aphids such sap from the plant, and long term can put the plant into stress. Certainly not helping the current condition of the impacted rose of Sharon.
For immediate relief, you can use any product containing acephate (tradenames - Acephate, Bonide systemic insect control) , malathion (tradename Malathion, Ortho Max Malathion Insect spray or Bonide malathion) or acetamiprid (Ortho Flower, Fruit, and Vegetable Insect killer).
Since they are wooly, be sure to thoroughly soak the scales to penetrate their "fur"