White powdery mildew on squash leaves

[Rachel W]

It started with my yellow straightneck squash but I didn't know it was mildew at the time. It looked like a white liquid had dried all along the outer edge of the leaves. A week later, there are little white solid circles all over the same leaves. That squash is in the most shaded part of my garden. My spaghetti squash is in the sunniest part of my garden and about 50 feet from the yellow swish. It is now starting to get the white circles on some of the leaves as well.
Today I went to the store to get Neem oil as I had read that it worked remarkably well on this mildew. Despite calling the store first and being told they had it in stock, there were no bottles when I arrived. They said they would have more on Thursday.
Has anyone had experience with using Neem oil to get rid of mildew? Did it work? Are there any other tricks? My main focus is to be organic.
I also read that it could kill bees. If I put it on at night will the bee killing effects wear off by the time it dries up in the morning? I have counted 6 different types of bees in my garden pollinating.
Please help me stay organic!
Thanks,
Rachel