I was given the recipe below by one of the folks at Native Roots as a means of at least slowing down powdery mildew on your squashes and melons. I will be trying it in the dome where it is just getting started.
32 oz. bottle filled with water
1 oz. vinegar
1 teaspoon of oil, veggie or peppermint
dash of dish soap
1 Tablespoon of baking soda
Mix well and spray on the leaves, top and bottom. Be sure NOT to do this in full sun or the heat of the day, the leaves are likely to get scorched from the sun shining thru the soap bubbles and oil in the solution. Late in the day is the best time so the sun is fading.
If you try it please let us know how it works for you. I have included a picture below of what powdery mildew looks like. It is extremely common this time of year, particularly when we are having such lovely rains. Most plants can continue to produce when afflicted but it does weaken the plant and will spread to all nearby squashes and melons.