A. You can use non-fat (skim) milk for your mildew. Spray it on in the cool of the day when your leaves have cooled down from the day’s sunshine. I just buy a half-gallon of it when I need it. If you plan to use the dry non-fat milk, the formula for that is one part skim milk powder to nine parts of water. I would trim all mildewed leaves off of the plant before I spray. Otherwise, the condition will continue to manifest itself since it is spread by spores.
Also good for squash leaves and cucumbers but remove bad leaves before you spray. Treat your plants every 10 days to two weeks. Also after every rainfall.
Mildew on tomatoes? Mix 2 tablespoons of wettable sulfur powder (use micronized so that it will flow) in 1 gallon of water and spray the leaves until runoff. Repeat every two weeks. When watering your veggies, never overhead water. This spreads disease and also washes off any control spray that you have put on your plants. ie. the non-fat milk or sulfur.
Sulfur is considered organic. You must use precautions when using it because, if inhaled, it becomes sulfuric acid in your lungs and will burn. So, just to be sure, use a mask, goggles, gloves. This seems like overkill but better safe than sorry. Sulfur does a very good job on keeping tomatoes mildew and russet mite free.
You can go to Google and research a product called Thiolux which is a micronized wettable sulfur. I believe Ortho also makes a wettable sulfur called Flowtox.