Answer: Mildew can look powdery or it can look fuzzy, but I don't think I would call it bright white. You might be seeing mealy bugs (they will hop) or you might be seeing the froth from spittlebugs, or you might possibly be seeing residue from foliar applications of fertilizer or a spray of some sort. It also could be bird droppings. I'm sorry I can't be more precise, but at least this might help you begin to identify it.
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