I have been battling it all year due to the heavy rains we've had and an infected punter of seedlings bought.

I eradicated the White powdery mildew on my strawberries and zucchini/squash plants overnight with this:

1 part whole milk
2 parts water

Spray on leaves, don't forget the underside. I saturated mine.

I did this in the late afternoon and in the morning all the leaves were glossy green again without a speck of mildew. And the fruit was back to normal. I couldn't believe it. I did a test patch on the button squash leaves and where I sprayed the leaves were clean and green in the middle of a mildew fest where I hadn't sprayed. It really worked for me.

I have to try this my columbine is suffering right now thanks for the tip

It does work. I found that I had to repeat it after about a week or so because it came back (much less than before) but since then it seems to have gone completely. Let me know if it works for you.

I sprayed them early this afternoon I can't wait to see them in the morning.

@AR Did it work

I may have applied the milk too late the columbine are are still alive but not thriving and the milk leaves a similar white residue on the leaves so I'm waiting till the weather becomes more consistent to see if it worked I did chop off some of the leaves to see if I could get some new healthy growth. I will follow up with a picture. Thanks for asking

Darn @AR I did mine in the evening so maybe that's why I didn't have milk residue (I had a little around the edges but it blew off in the wind.

Some of the columbine are still blooming and some are still growing so I'm just going to leave them and see what happens.None of the other plants seem to have it.

Some of that damage looks like columbine leafminer (blotch mines rather than serpentine). Is there powdery mildew in addition?

Very well could be They are a mess and just keep trying I feel for them.I'll have to do more of an investigation. Thanks Sue