Disease risks based on this week’s rain events

(I’m still at a meeting, so, I will make it quick.)  At Winchester, the series of rain started around 2 AM on this Monday (5/17/10), it was not a continuous rain, but we had frequent enough rain events during Monday, Tuesday, and this morning to keep the relative humidity high (>90%) until ~9:30 AM today.  During Tuesday, there was a moment when the RH was little less than 90%, but it was still in high 80’s.  Thus, I would say this rain event accounted for about 55.5 hours of wetness and average temperature during this period was about 58F.  Thus, it was long and warm enough for downy mildew, black rot, and Phomopsis.   Some of us are expecting bloom very soon.  Please remember that the critical time for downy, black rot, and powdery mildew berry infection is from bloom to 4-5 weeks after bloom.

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