Powdery mildew

A white to grey powdery coating on leaves and stems, thriving in warm days with cool humid nights. Common on cucurbits and peas late in the season.

Dusty white patches, first on older leaves, that spread until leaves yellow and dry.

Remove the worst leaves. A milk spray (1 part milk to 9 parts water) or potassium-bicarbonate spray, applied in the morning, slows its spread organically.

Space plants for airflow, water at the base not overhead, and choose resistant varieties. Avoid crowding late in the season.