It has come to light recently that the spraying of MILK onto leaves et al affected by mildew can help.
And you know what.........they don't know why....except they suspect it gives the plant immunity to further attacks.

Mix up a 10% solution.....1 part 2% milk...9 parts water and spray all surfaces of your plant.

They choose the 2%...or skim milk formula due to thinking the more fat the milk has, the less immunity.

try reading the post about 'Sinbad' and mildew. there are soem helpful hints there.

-ming