PM is definately enhanced and spread by over head watering.as for the beatles and vine boars, they all must have migrated to zone 7. we have had an awful time with them. and the stink bugs were unbelievable!

I would not worry to much about composting the mildew infected plants. since the mildew spores are most likely present in your garden soil so you will get a reinfection if conditions for mildew growth are present. the best solution is using mildew preventives or control sprays.
there many organic application to use to this end. Which I will not detail here.