Question
Our knockout roses have been getting these "white spots" on their stems (stems only). The white spots are powdery like and "poofy", almost like the little white web balls that you see spiders make when they wrap other insects. My research has only found information on black spots, rust, powdery mildew, and aphids. Do you know what these white spots are and how to get rid of them?

Answer
Those white spots are scale insects and can be scraped off if there isn't a lot of them. Just take a kleenex and a blunt knife and scrape them off into the kleenex and then put them  into the garbage. If there are a lot, here is some more information on them for you. Plus just google rose scale insects and lots will come up.
http://www.virginiafruit.ento.vt.edu/RoseScale.html