Powdery mildew is a fungal disease that results in a powdery gray or white coating on the leaves and stems of infected plants. It starts out as a few spores on the leaves, and quickly spreads, eventually yellowing the leaves and causing premature leaf drop. Chemical control is possible with fungicides such as triadimefon and propiconazole. Another chemical treatment involves treating wheat with a silicon solution or calcium silicate slag. Silicon helps the plant cells defend against fungal attack by degrading haustoria and by producing callose and papilla. With silicon treatment, epidermal cells are less susceptible to powdery mildew of wheat.