Posted: 19/07/2014 at 10:30
Okay...new tricks time again, OL.
A dilute spray of milk has been known to be an effective treatment for mildew on courgettes (and marrows of course) but as the others have said, it doesn't harm the plants or damage the fruit.
The dilution is 1 part milk to 2 - 3 parts water. The solution is then sprayed on the plant's leaves every 10-14 days.
It works best as a preventative, rather than a cure, which makes it hard to determine whether it actually works since you don't know if your plants would have gotten it anyway.
Personally, I couldn't be ar*sed.