Question: what are the white spots on my houseplants?
Answer: Powdery mildew on houseplants is a fungal disease. Initially, it produces circular powdery white spots on the foliage of plants. ... The indoor powdery mildew requires temperatures around 70 F (21 C). It occurs when there is poor air circulation, low light, and unlike outdoor powdery mildew, thrives in drier conditions.