Powdery Mildew

[meadowflower]

Hello!

This is the second year we've had our home. There was a vegetable garden area already laid out when we came. Last year was an extremely wet summer and a very bad growing season here. Early season stuff was great - yellow and green squash, some cukes, etc. However as summer rains came consistently, I got powdery mildew on EVERYTHING (as well as blight on the tomatoes).

This year, our tomatoes are great (no blight). However, we had powdery mildew almost from the get-go, even though we did not water at night, didn't keep the ground wet, etc. Our only crops that came out well were green beans and tomatoes. All of the pumpkin, squash, cucumbers got powdery mildrew.

This stuff may have been in the soil/plants before we moved in, or maybe we didn't get it all out last year. I don't know. Is there some way we can treat (natural, non-chemical) the soil to minimize its return next year? We don't have much growing space but I am thinking of letting that plot sit for a year or two and just do my growing in a different area of the yard. 

Thanks for any tips!