At Winchester, we received 0.25 inches of rain on 4/19/11.  It started from 9:20AM and lasted until 4:20 PM or so, and the relative humidity was above 90% until 5:00 PM.  Thus, we had about 7 hours 40 min of wetness with the average temperature of 55F.  It was long enough for light infection of Phomopsis (= low risk), but it was neither long nor warm enough for black rot.