The infection usually starts off as circular, powdery white spots which can affect leaves, stems and sometimes fruits. It usually covers the upper parts of the leaves but may grow on the undersides as well. The fungus hinders photosynthesis and causes the Leaves turn yellow and dry out and some leaves might twist, break or become disfigured. In the later stages, the buds and growing tips become disfigured.
Fungal spores overwinter inside leaf buds and other plant debris. Wind, water, and insects transmit the spores to nearby plants. Even though it is a fungus, powdery mildew can develop rather normally in dry conditions. It survives at temperatures between 10-12°C, but optimal conditions are found at 30°C. In contrast to downy mildew, small amounts of rainfall and regular morning dew accelerate the spreading of powdery mildew.
Foliar sprays based on sulfur, neem oil, kaolin or ascorbic acid can prevent severe infection.
Always consider an integrated approach with preventive measures together with biological treatments if available. In view of the number of crops that are susceptible to powdery mildew, it is difficult to recommend any particular chemical treatment. Fungicides based on wettable sulphur (3 g/l), hexaconazole, myclobutanil (all 2 ml/l) seem to control the growth of the fungus in some crops.