Yuck! Powdery Mildew. I may as well expect this unwelcome visitor each year and learn to deal with it. Either that or squash beetles or both. My family wants to eat squash, melons, cucumbers and such. So I will learn to deal with these issues.
Some varieties of plants may be resistant to powdery mildew. It loves crowded conditions, shade, humidity, poor air circulation. Watering in the morning instead of night may also help.
Powdery mildew is a fungi of the bad sort. It overwinters in plant debris and produces spores in the spring. These spores are carried by wind, water and insects. Just imagine little bugs tracking spores across your plants like kids tracking mud across your freshly mopped floor.
Powdery mildew is specific to the plant it attacks. I’ve never had a problem with it on my tomatoes, peppers, herbs, cabbage, broccoli. It seems to love my viney plants such as squashes, melons, cucumbers and also sunflowers. It left my ground cherries alone.
I looked online for various solutions. Last year I tried a milk/water solution. I’m not sure how well it worked, possibly I should have started sooner.
Earlier this year I bought a backpack sprayer for spraying good stuff on my fruit trees. Trying one of the baking powder solutions looked like a great way to test out my sprayer. The sprayer directions weren’t that clear, but I figured it out. Love the backpack sprayer, wished I’d gotten one a long time ago.
Powdery Mildew Spray
1 Tablespoon baking soda
2 Tablespoons vegetable oil (I’d use neem oil if I had some on hand)
1 teaspoon dish soap
1 Gallon of water
I mixed the baking soda with 1 qt of hot water and the oil and soap before pouring into the sprayer, then I added the other 3 quarts of water and sloshed the container around. Plants had been watered and the worst leaves picked off. Now I sprayed the effected plants with this spray. If all goes well I’ll spray these particular plants weekly with the baking soda solution till the danger is past.
Checking the plants a few days later and they look much better. A couple of places I missed and they still have the powdery mildew. Rest of the plants look quite happy. For me, the baking soda spray worked much better than the milk solution I tried last year. I did not notice a decrease in pollinating insects after use.
To see how this works for you, you may want to test a small area first.