I use plain vitamin d milk in a sprayer ......just liberally spray it on .
You may do a 50/50 mix water,milk.
It is a Jerry Baker the garden guy remedy..
And it is organic!...it does work and you probably have some in the fridge.
Here is a link to an article that is of interest.
http://www.growveg.com/growblogpost.aspx?id=242
I spray my Cukes and Monarda when they get it during the humid spells in August.