I have 3 Mandeville's, and all of them have white fluffy spots on them. I have trimmed them back to about 18 inches tall and set them in the bathtub and sprayed them with water washing them very good and then sprayed them with Insecticidal soap but the white spots have come back. I am afraid this will kill the plants. Any information will be appreciated.
It's sort of difficult to tell from the photos, but I'm thinking that looks like scale. In that case, NEEM oil is the treatment of choice. Follow the directions on the bottle, including the re-application timeline, and you should be ok.
I agree with speediebean, it appears to be scale. Neem oil works well. A Q-tip dipped in rubbing alcohol and dabbed on the scale works too if the infestation is small. If the infestation is widespread, Neem oil is easier, IMHO.
