A friend of mine brought me some leaves he is concerned about. the bottom part of the leaf is coated in what looks like sugar granules. They don't wipe or lick off (I tried both) when you look at them thru microscope they look like little drops of water, no color at all. What could this be and how can we prevent this from happening? I originally thought it was mold but I though mold was powdery....maybe I am wrong. If anyone has any suggestion to throw my direction I would much appreciate it. It is just on the under part of the leaves....none on top of leaves.