Root Rot

Question

Are one of the symptoms of root rot what looks like whitish powder?

Answer 1

No, the white powder is probably powdery mildew, which thrives in the same conditions that root rot does. These articles will help:
https://www.gardeningknowhow.com/problems/get-the-cure-for-powdery-mildew.htm
https://www.gardeningknowhow.com/plant-problems/disease/powdery-mildew-homemade-and-organic-remedies.htm