Prevent powdery mildew: 1 gallon water 1 tbls each baking soda, vegetable oil, and dishwashing liquid Mix together and add them to a spray bottle. Spray your plants weekly, preferably on overcast days to prevent it from burning the foliage.
Mildew on Rose Leaves Baking Soda Spray: 1 tbsp vegetable oil 1 gallon unchlorinated water 1 tbsp apple cider vinegar 1 tsp Listerine (yes, the famous mouthwash, not mint flavour, just regular) 1 tbsp liquid soap 1 ½ tbsp baking soda Pump sprayer (large)
Prevent and Kill Blight & Powdery Mildew With Baking Soda - This is one fool proof method to preventing, and even STOPPING the spread of powdery mildew, and blight. That is by using the power of baking soda.