Kevin, I'm afraid my experiences with powdery mildew don't offer much as far as getting rid of it.
I think a lot depends on having plenty of organic matter in the soil; for plant nutrition of course, but even more so to maintain moisture.
I find powdery mildew takes over when plants are water stressed. Like most people's summers, later it gets, the drier things are.
But by the end of the season at my place, when it really starts to slow down the zucchini, I'm rather relieved!

Understanding why Powdery Mildew appears often helps with control. Sulfur is effective if applied before signs of PM appear while other controls can be effective when properly applied.
Baking Soda (Sodium Bicarbonate) mized one teaspoon per quart of water, Fat Free Milk and water mixed 50/50, Potassium Bicarbonate, and Neem oil have all been effective at controlling PM, but not at curing the problem. Since the spores that cause PM are blown in on the wind there probably is nothing that will cure this problem.

Here is a link that might be useful: About Powdery Mildew

First, you need to understand that you can't cure powdery mildew - once it is present (and you see the symptoms), it's present and the best you can expect is to control the spread. Period.

Fungicides are prophylactic, not curative. They can sometimes prevent the disease, will often limit the spread or contain the disease but they will not eliminate or "fix" existing diseased tissue.

Powdery mildew is most often a cultural ailment. It arises typically in late season when temperatures are warm, soils are dry and humidity typically high. Lack of good air circulation can exacerbate the condition. Not a lot one can do about temps or humidity but making sure the soil is adequately moist and improving circulation can go a long way to slowing the disease. Knowing what plants are most susceptible and treating before you see any signs can help. FWIW, with most woody plants, PM is more of a cosmetic issue than a serious threat to plant health. Also, PM spores cannot live in water - hosing down the plants early in the day (so there is adequate time for the foliage to dry properly to deter other fungal issues) can help as well - you can actually wash the spores off the leaves.

The reason milk is often recommended - and with good reason - is that it is a natural anti-fungal/anti-bacterial agent. It also contains lactic acid, which alters the pH of the leaf surface and makes it inhospitable to the fungal pathogen. This is the same principle behind the use of baking soda as well. btw, it doesn't make any difference what formulation of milk you use - powdered, fat free, high octane - it all works the same.

So, What you all are saying is milk and other remedies CAN keep the population of spores down if I start treating the foliage with said remedy prior to actually SEEING any spores??

Kevin

Yes, any fungicide regsistered for PM, including those home remedies like the milk, baking soda, etc., will help to prevent the spread of fungal spores to unaffected foliage and if applied prior to infection (usually before the symptoms are evident), should prevent the problem altogther.

But do follow good garden sanitation and proper cultural practices as well - all the spraying in the world won't help significantly if you are just welcoming the disease by offering poor growing conditions.

Milk works very effectively, provided you apply it at the appropriate time. The lactic acid it contains alters the pH of the foliage and makes it inhospitable to the development of fungal spores. Also the enzyme lactoperoxidase contained in milk is antipathogenic and is effective in killing of a range of plant pathogens, inlcuding PM.

I have used a mixture of milk and water (a 50/50 mix of fat free milk and water) to control Powdery Mildew. I have not seen the same results using other ( whole, 2 percent) types except raw milk does have the same affect. Raw milk is not as easily assessable as skim milk. Using raw milk as a deterrent was discovered by a couple of researchers in Brazil looking to control tobacco mosaic several years ago.

I have also used a mixture of 1 teaspoon of Baking Soda in 1 quart of water just as effectively.

Milk is alkaline which is why it might work. From all I've read, powdery mildew thrives in an acidic environment. This year has been exceptionally bad for powdery mildew here. It devastated my phlox, killed my poppies, and attacked even the wild black-eyed Susans. Later this fall I plan to dump bags of crushed limestone on the gardens that were hardest hit in hopes of making life difficult for mildew next summer. I think nothing cures it, but measures can be taken to make the environment less friendly to it.

Dumping limestone on the soil will have no effect on the development of PM and will likely screw up your soil pH. PM doesn't survive in the soil - it needs living plant tissue - so soil treatments are a waste of time. The development of PM is an environmental condition determined primarily by weather - warm, humid nights and dry soils (as are common in late summer) are ideal conditions for pathogen incubation

It would be far more practical to treat susceptible plants before you see any signs of the disease. And to follow the cultural pactices that are recommended to avoid PM in the first place.

ETA: milk has a pH of 6.5 to 6.7, so slightly acidic.....not alkaline. And lactic acid, which is what is the effective PM control in milk, is very acidic at a pH of 2.4. It is this extreme acidity that makes the PM disinclined to develop or spread.

Milk certainly does contain lactic acid....some milk presentations more than others.

"Lactic acid develops in cow’s milk as a result of bacteria fermenting (breaking down) the lactose. Freshly expressed milk does not contain lactic acid. It is only after a short period of time that the concentration builds up due to the input of bacteria. This means that lactic acid can be used to assess the quality of milk and its state of preservation. It can also be found in dairy products such as yoghurt, cheese, bread and beer."

The comment ""Lactic acid develops in cow’s milk as a result of bacteria fermenting (breaking down) the lactose. Freshly expressed milk does not contain lactic acid. It is only after a short period of time that the concentration builds up due to the input of bacteria." has the exact same meaning as "Milk doesn't contain lactic acid. Lactic acid is produced by lactic acid bacteria." So I believe you have incorrectly asserted "Milk certainly does contain lactic acid" when you should have instead replied "Correct" as milk only contains lactic acid once bacteria have created it, as clarified in your quote "Freshly expressed milk does not contain lactic acid. It is only after a short period of time that the concentration builds up due to the input of bacteria."

I have eradicated PM from multiple cultivars using horticultural oil sprays. Three applications three days apart eradicated my infections. Of course you need to also clean your floors, walls, and fans which can collect and spread spores, and remove any disease reservoirs as well as filter incoming air so as to not introduce spores which are endogenous to the environment