Powdery mildew may look harmless, but it can prove fatal to the many plants it affects. The white or gray fungus has a consistency similar to that of talcum powder and is generally first seen growing on the bottom of leaves. Not only will powdery mildew severely damage the plant, it will spread to other vegetation, infecting it with the fungus. To ensure the plant has a fighting chance against powdery mildew, use milk for an all-natural and organic fungicide.
I thought I had powdery mold...it was spidermites, that's when I needed the neem oil...good luck..and look at the bottom of your leaves with a magnifying glass for little dots making webs and sucking the life outa your plants..
neem oil is a preventive. once you get pm neem will not help. Serenade is a fungicide, and organic, that works very well against pm and many other diseases. GL