Powdery Mildew

Powdery mildew is a given here in Hawaii. The air carries a lot of moisture. Plus a lot of various fungus and mold spores. So rusts and various mold diseases regularly cycle through. Some years are worse than others. And I actually saw one year where there were no fungal diseases, but it was our worst drought year too since we moved here. That's no longer the situation. Things are back to "normal" and we see bouts of various fungal diseases routinely. 

I've tried battling powdery mildew in the past, usually with zero luck. I've learned a few things since then. 

1- When possible, grow varieties that have some resistance to powdery mildew. 

2- You can't cure powdery mildew once it's there. 

3- Start treating early to prevent powdery mildew. 

I still haven't settled upon my preferred line of attack. I tried the milk trick, but it failed. But then, I didn't start early enough.  I tried the urine trick and also failed. But again, powdery mildew had already infected the plants. Eventually the light bulb went on and I realized that I need to prevent powdery mildew, not try to cure it. 

I plan to try experimenting with various treatment methods, but for now I have resorted to sulfur spray when I first saw a few early dots of mildew on the greenhouse plants. Spraying once a week has kept the powdery mildew in check for most of the plants.....at least well enough for them to produce their fruits (cucumbers, squash, and now tomatoes). I plan to continue with the sulfur for now, but later this year I'll purposely plant susceptible plants out in the main garden just so I can conduct an experiment. 

What to use? I've seen suggestions for...

...diluted milk

...diluted urine

...compost tea

...sulfur 

...neem oil 

...baking soda (I added this after "P" emailed me)

...various commercial chemical fungicides 

Ideally I'd like to come up with a spray that this farm can produce for itself, as opposed to buying.

What poor victim will I use in this experiment? I'm thinking of summer squash. I've seen them succumb before the poor plant even gets its first female flower. Most open pollinated cucumbers are almost as bad.