Powdery Mildew looks like small cotton balls on the plants vine and leaves, or white spots on the plants leaves.
A Natural Remedy:
3,5 Litres Water
1 Tsp Baking Soda
2,5 Tsp Vegetal Oil (Olive oil works well)
2 Tsp Soap
Blend and water for approximately for a week. Water early mornings or after sunset.