The best way, in my experience, is preventive program. That is, spraying regularly, (say every two weeks) with Daconil or similar anti fungus sprays(NEEM oIL). If you do that, you can prevent it. This requires a determination and discipline that not many of us have.
As the old saying goes: AN OUNCE OF PREVENTION IS BETTER THAN A POUND OF CURE.
But once you detect PM, then you have to fight it but you can never get rid of it.

Last time I posted this, there were cries of outrage, but I've found that Immunox [the kind w/o insecticide] works very well against PM on curcubits. I sprayed early in the summer and didn't see a spot of mildew for months.

ltiton ... I have used both daconile and Neem oil. They keep PM in check but never get rid of it. I'll try Immunox next yeat. Does it come in concentrate so you can make your own mix? The Ready -to-mix ones are not economical, I think.

I understand and can relate to your experience when the dew comes. Downy and powdery mildew needs wet leaves to take hold, so good air circulation is key to keep the leaves dry and prevent onset. I avoid watering on leaves for instance. At the first signs of onset, i use a 30/70 milk/water solution and spray the leaves thoroughly. This helps a lot in my experience and i do this every 5-7 days. For me this is a good solution as it is a remedy without chemical sprays and only costs a couple of 100ml of milk.

Ralph

Ralph .... good point to keep leaves dry and provide air movement. But it is hard to do with things like squash vines lying on the ground, dew , rain, . I can manage tomatoes better in that respect.

Water /milk is good too. Actually I like low fat instead of skim, because the fat/oil creates a more lasting barrier. I would even prefer 50/50 for that reason. I think that is what (maybe) NEEM OIL does too. There are few insect sprays with some kind of oil.

The point is, not to give the fungus a chance to multiply

Absolutely agree it can be difficult to air with vines on the ground seysson.
I have tried a couple of things to mitigate that with good success.
First one was to actually have the pumpkins/squash climb up a trellis instead of on the ground. I found this can work but requires a bit of work as the vines don't naturally climb on a lot of varieties and also depending on the size of the fruit, you will need to support them as they get bigger.
A second thing i have done is to make sure that later in the season when mildew normally hits, is to remove the tertiary vines that start to come as these will suck energy from the vines with fruit and generally come too late in the season to bear fruit themselves. They also cause the leaves to become dense and in my mind help the mildew take hold.
Ralph

I tried a version of the Cornell formula on a few squash plants. In a quart of water I added 1 tsp baking soda, 1 1/2 tbs cotton seed oil, 1 drop dish washing soap. It seems to be working and as a bonus the plants that were previously damaged by SVB are no longer wilting. The oil on the leaves is conserving moisture.

I spray every 7 to 14 days. It doesn't completely eliminate it but keeps it under control and the plants fruit very well.

Thanks for all the replies, what a great forum.

I will look into the various sprays you have suggested, like to go organic if possible but this is serious, the squash were basically wiped out this year.
Late in the year I tried just spraying with water each morning to see if that would wash it off but the damage was already done.

Housekeeping, housekeeping, housekeeping! PM spores overwinter in fallen leaves, vines, etc. Don't forget the importance of that step....it's crucial.

PM does NOT need free water in order to germinate; dew does NOT increase its activity. As a matter of fact, the spores can be sprayed off with plain water if caught before the cells are infected.

I use two things to prevent PM on problematic veggie plants (aside from housekeeping) . The first is Neem oil, but that can't be used when the temperatures get too hot. The second is 'Surround ', a wettable kaolin clay powder.

PM spores cannot penetrate through a fim of Surround '. It also has the added benefits of hugely reducing insect pest damage, as well as heat and sun stress. I love the darned stuff.....and it is absolutely organic.

Surround is a protectant, a physical barrier to windborne disease propagules.

The Cornell formula - would any vegetable oil work? Canola for instance. We don't see cottonseed oil much around here.

I'm definitely going to try spraying for PM next year. I have already removed the plants and will pick up all the leaves left behind. Will remove tertiary vines as well.

I lost my cucumber plants to blight but that's another story.

Thanks.

Frances

I'm not sure Canola oil from the kitchen would work. Some type of horticultural oil is usually used. You can read about it here:

Here is a link that might be useful: Colorado State University

Cotton seed oil is just more saturated. Sunflower seeds oil should be close enough. They are originally solid.
The oil itself and the soap do not destroy the spores. They just create a film/layer that spores cannot get in. It is the same idea with milk and water. So, IMO, low fat milk is better that skim, because of the oil's film and sealing effect.
Neem Oil, I think,, does the same when it comes to PM. But it also repels some insects. Again,, I don;t think it kills anything .

Thanks for the link, danzeb. Checked it out and at the bottom of the page, 3 veg oils are mentioned: cottonseed, soy and canola. It looks as though cottonseed is better at controlling insect pests than the other 2.

If I can't find cottonseed oil for sale here, I think I will try the canola and will post the results. Cheers.