mildew

Question

Mildew on soil of houseplants white.

Answer 1

If this is powdery, it is powdery mildew. Here is more info: https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm

If it's mold on the soil, this article will help with that: https://www.gardeningknowhow.com/houseplants/hpgen/preventing-mold-in-the-soil-of-a-houseplant.htm