I am having the same problem. I read on the internet that sometimes using a mixture of milk and water sprayed on the plants weekly will keep powdery mildew at bay. I don't know if it works or not, but this morning I went out and sprayed all my spaghetti squash, zucchini, and pumpkins with the stuff. You might want to try it. I'll let you know how mine does.

If you want the specifics, I wrote about it in my blog today (linked below).

Here is a link that might be useful: My blog post about powdery mildew

Organic Mamag,

Thanks for the tip. I'll give it a try on my remaining squash plants. At this point I'm not sure it will work cause the vines and leaves are already starting to wilt. It was cloudy and humid today. I guess tomorrow I'll spray them with alkaline water from my water ionizer mixed with some organic whole milk.

Thanks,
Jerry

Did it work? I have the same problem. I have up chicken wire and I noticed the fenced areas where the pumpkin grew up is not as affected. I am trying to figure out if I should get rid of all the infected leaves to save the few good leaves we have. . . I sprayed with fungicide. I will try the baking soda--but I heard not to do fungicide and baking soda at once, so I will wait. I could try the milk as well. I'm holding out hope that I can save the three pumpkins that are only about four inches big right now. Also, if the mildew spreads, is it okay to plant pumpkins next season in the same space?

I started using the mixture of water and milk (9 parts water 1 part milk) last year it works great,but you have to get after the mildew AS SOON AS YOU SEE IT or it becomes a real problem.
I read about this mixture in our papers gardening section.A recomadation use 2% low fat milk

I used the milm/water combo and added 1 tbs non antibacterial liquid soap to break the water tension. at least things are not worse.

I've given up on treating the mildew infected plants. Hopefully whatever survives and produces seeds will have a genetic makeup with some mildew resistance. With all my neighbors growing squash and mildew, there's no way my plants can remain uninfected for long. The soap is great for aphids I've found. Milk attracts the neighborhood stray cats and they do a number to the roots of all my plants. Them and the squirrels are my biggest problems besides mildew, and SVBorers.

Yes - try the mixture of 1 part skim milk to 9 parts water. BUT spray that first thing in the spring when your plants are beginning to grow - and then just spray again when you think of it! If you use whole milk you risk getting a bad smell. I have used this mixture on all my gardens and flower beds and haven't had mildew and black spot in over 5 years yet my neighbor has a terrible problem with both - on everything!!! Others have told me they won't use it as it sounds like a witches brew! go figure. Never had a problem with cats! Also if you soak your seedlings, soil and seeds with a solution of equal parts hydrogen peroxide and water your plants will thank you - it seems to give them a great start and the plants seem stronger.
Good luck.

I also had a problem with PM on my containered acorn squash this year. I used a fungicide but it only worked marginally. The plants did stay alive enough to get a few squash, though.

I was wondering as well if I should be careful not to use any of the same dirt and sanitize my containers to delay the onset of the PM in next year's planting. Does it really matter?

I do think I'll try using the milk/water spraying from about mid-summer (when the PM first popped up this yeaar) to try to delay its progress. I like this method a lot more than using chemicals.