Powdery Mildew is a disease infecting Sunflower especially during the flowering and grain formation stages affecting crop growth and yield.
The disease appears on the upper surface of leaves in the form of pale yellow or pale brown minute discoloured specks from which powdery mass radiates to all sides of leaves. Heavily infested leaves dry and shed prematurely. Soon these specks get covered with whitish powdery mycelial growth which increase in size and develop to cover much of the plant area with white powdery growth. Gradually, the infection spreads to other parts of the plant. The disease is prevalent more under dry conditions especially at the end of the winter months.
[source : TheHindu]