I have a ponytail Palm that I've had for years and is fairly large. It has this white fungus looking stuff on it. I have attached a picture of it. It is mostly in the crown areas of the plant. I asked a local nursery what to do, and they said to spray it down with rubbing alcohol and wipe as much of it off that I could and then apply a pesticide called "eight". I did this several weeks ago and it looked good for a few weeks but now it's back and it's worse!