iirc Immunox is considered the fungicide of choice for PM on grapes.

I would first check to make sure it is not downy mildew. Powdery tends to like drier weather, downy likes it wet. If you have powdery you are lucky, many things will work on it. I found summer oil to be highly effective. Downy is much harder to deal with; I used copper for downy on my organic grapes. There are also synthetics for it, mancozeb if memory serves.

Scott

Will check on the difference of downy/vs powdery mildew. Thanks Scott and Itilton. Mrs. G

what does iirc mean?

iirc= If I recall correctly

Thanks, never have been into abrevs.

Scott thanks for telling me there are two types of powdery mildew. (downy being the other). What I have are only two leaves with powdery mildew and they were not totally covered by the white powder. I cut them off and will spray with immunox after it stops raining. Raining and more rain! Two more days of the horrible rain is predicted., but, the temps dropped into the high 60's today. A twenty degree drop over night. Mrs. G ps. weather has been horrible this summer so far.