i had it really bad last year. one treatment is to spray them with skimmed milk : water mix 1:10 and spray that on. the slight acidity of the stuff slows the mildew down, but wont kill it off. i finally cut off a lot of the bad leaves and the pumpkins stopped growing, the fruit that had already set was unaffected but it ceased to make any new babies.
your cucumber might catch it, so watch out
