Powdery mildew

White powdery coating spreading on leaves and shoots.

Updated on 2026-07-17

Overview

Powdery mildew is a fungal disease caused by several Erysiphales species. It thrives with temperature swings and high night humidity, typical of greenhouses and balconies in autumn.

Differential diagnosis

White coating that dusts off easily = mildew. Coating that stays put = limescale.

Natural remedies

Baking soda (5 g/L) + a few drops of soap, sprayed every 5 days for 3 weeks.

Treatments

Micronized sulfur on cool (<25°C) shaded days to avoid phytotoxicity.

Prevention

Ventilate, space plants, avoid wetting foliage in the evening.