Try wiping off this dust and see what happens in a few days. If it appears again, it may not be dust but powdery mildew! Powdery mildew is a rapidly spreading fungal disease of plants. Initially, a fine white coating resembling flour or powder appears on the leaves. It can be easily rubbed off with a finger and even mistaken for ordinary dust. Not only do the leaves become white, but also the stems and flower stalks. If, after a couple of days, you will not notice an abundance of dust on the maple, then you can not worry. To help your maple leaves breathe better, you can collect the dust with
a dust collector.