Powdery Mildew looks nasty but it generally won’t kill your plants. However, it may reduce the yield. Once you get it, you can’t get rid of it, but you can control it with a couple of simple measures.
• Spray with diluted cow’s milk. Mix 1 part milk with 9 parts water and spray the stems and tops of leaves with the solution. Skim milk will tend to be less stinky since it doesn’t have any fat in it, but any milk will do. Reapply after rain.
• Spray the leaves with baking soda. Mix 1 teaspoon in 1 quart water and add a tiny squirt of dishwashing detergent to help make it stick. This raises the pH, creating an inhospitable environment for powdery mildew. Reapply after rain.
At the end of the season, do a thorough garden clean-up. Dispose of the worst plants/leaves and do not compost because the spores may overwinter. Next year, try and space your plants a little farther apart. High humidity (gee…what’s that??) and crowding don’t allow your plants to dry out during the day which contributes to the spreading of the disease.
To read more about powdery mildew, check out these links…