I've used baking soda for mildew on my bean and squash plant leaves.. Mix 1 tablespoon per gallon of water and apply with spray bottle... Some people add a 1/2 teaspoon of dish soap... I apply if plants show symptoms of powdery mildew or after a humid rainstorm.. I noticed that something they put in "city" water slightly hinders mildew also..

That's interesting, because I live a few towns south of you and last fall also had powdery mildew on my beans for the first time ever. I read about it a bit on UC Davis' site, which said that:

-it grows best in shady, warm conditions (60-80F)

-unlike other mildews, it doesn't need water to flourish, and is actually inhibited by moisture

-spraying infected leaves with water in the morning helps a bit (I tried this and it did slow the mildew down some, but used more water than I would like)

-improving air circulation helps

-horticultural, neem, or jojoba oil help with mild-moderate infestations

So it sounds like the drought weather is to blame for the increased mildew we're seeing. I've talked to other gardeners who swear by spraying with whole milk (anywhere from 10-40% milk solution), so that might be worth a shot too. I'm about to give the baking soda spray a try on my sad spotty pea plants.

Thanks for the responses! I did check out the UC Davis info earlier, but it is still reassuring to have others in the area say they've had a similar experience. The raised beds I use for beans (& other sun-lovers), are in full sun, but I didn't try any of the suggested sprays last year.

This is really good info, I too had my first run in with powdery mildew on my beans last year. This will serve me well this year. Hopefully I won't need it though.

Jim Myers at OSU is working on tolerance. It will take several years and may not yield significant results for several more years. The only negative is that he is working with bush blue lake beans, not pole types.

Resistance is present in Runner Beans but not in Phaseolus Vulgaris which is the common bean.