Powdery Mildew is not a disease that relies on heat and humidity. "Powdery mildew spores are carried by wind to new hosts. Although humidity requirements for germination vary, all powdery mildew species can germinate and infect in the absence of free water. In fact, spores of some powdery mildew fungi are killed and germination is inhibited by water on plant surfaces for extended periods. Moderate temperatures (60ð to 80ðF) and shady conditions generally are the most favorable for powdery mildew development. Spores and fungal growth are sensitive to extreme heat (above 90ðF) and direct sunlight."

Here is a link that might be useful: About Powdery Mildew

Hi Kevin,
Yes, please do keep us updated on your success with the Potassium Bicarb. As a fellow San Diegan, I completely agree with your assessment regarding the obvious influence of humidity on the emergence of PM. Also, I do believe once you have it in your garden, the spores will probably return at some point year after year, at least that has been my experience, and will require prompt and ongoing treatment to keep it well under control. I have had very good results with Neem Oil, but it is pricey and I would love to find a reliable, all-natural, cheap alternative that is kind to the plant, my family's health, and beneficial insects.
2 questions: Did you spray at night? How much potassium bicarb did you use per gallon of water?

Kassie2: Hey neighbor! :)

Yep.. at dusk. And I added 4 tsp/gal.

Regarding my "assessment", I only call 'em as I see 'em. ;)

I agree about the neem--- it's amazing how fast a 10 dollar bill goes. Not only that, but I am also trying to do the whole beneficial insect thing, and I'm not to sure about HOW much damage neem does to them.

Will update shortly. Going to do another treatment tonight.

Kevin

Wondering, did it work?

The Potassium Bicarbonate does control Powdery Mildew, just as the research done at several agriculture research universities indicated it would. Potassium Bicarbonate is somewhat better than Sodium Bicarbonate (baking soda), Neem oil, or a 50/50 mixture of fat free milk and water.

kimmq is kimsr