It sounds like mealy bugs to me,, , You can wipe off the entire Plant with Rubbing alcohol removing every Piece of white,, then as a follow up the next few days with 50% rubbing alcohol & 50% water and spray your plant.
Remove the plant away from other plants,, IF it was in very close proximedy I would also spray the other plants as a precaution .
OR,,, I would do as Jonni13 mentioned
I would try a spray bottle full of water, a few drops of insecticidal soap (or dish soap) and a tablespoon or so of baking soda. Spray/saturate the plant and watch to see if it helps. Repeat every few days without over-watering the soil if possible.
( the baking soda is the component for fungus. IF you feel you have mealy bugs and there are area's of blackening due to advanced stage of damage then a fungus has developed as a result of extensive damage)
but the most important thing to do first is to remove all the white ,,* mealy Bugs* with either q-tips with alcohol or or an old tooth brush dipped in alcohol.
By your picture and description I feel it's mealy bugs, when I see the first indication of them I've always used rubbing alcohol and wipe entire plant from base to tip, top and under leaves,