Irene stayed little longer than I expected in our area. At the end of Sunday, Winchester area received a total of about 0.5 inches of rain. I was monitoring the RH for last 2-3 days, but it was below 90% (actually it was 60-70% in most of time between rains). It was probably because of high wind due to Irene. Based on this information, the risk of Botrytis is not high; however, as with any precipitation events, it varies dramatically even between short distances. (For example, our AREC station received 1.2 inches or so from Irene.) Thus, please check your local weather service.
Grape Disease Management Tips from Mizuho Nita (Grape Pathologist at Virginia Tech)