As you probably noticed, the sun is out! And grape vines are moving fast. Our Chardonnay and Cabernet sauvignon has moved quite a bit as well. About 7-90% are 5-7 inches (E-L 12) and about 5-70% are 5 inches (E-L 12) for Chardonnay and Cab sauvignon, respectively.
Yesterday (5/07/09), Winchester area had a brief shower (0.12 inches) from 10:25am (64.4F) to 12:00pm (64.4F), and the RH was >90% until 1:00pm. And then a very short thunderstorm from 3:40 to 4:00pm (69.8F). The first event was bit short for Phomopsis and black rot infection events; however, it was probably enough for powdery mildew ascospore discharge and downy mildew infection event. A mild temperature range favors both mildew pathogens too.
Some of varieties are probably getting closer to the bloom, and you need to start thinking about these mildews. 2-3 weeks pre-bloom is the start of critical period for downy mildew rachis and berry infection. Make sure that your spray program has something against downy mildew (mancozeb, captan, etc for protection, and metalaxyl (Ridmil Gold MZ etc) for curative and/or protection). Once again, the risk of a disease will depends not only on the local weather condition but also on disease history of your vineyard, training system, variety etc.
We are expecting see yet another rain events today and tomorrow. I hope that you had a chance to apply whatever you needed.