Disease risks based on Sunday-Monday rain events

At Winchester area, the second series of rain started around 5:20 pm on Sunday, then it continued on and off until around 8:30 pm on Monday with about 0.17 inches of precipitation.  Thus, there was about 27 hours of wetness with average temperature of 58F or so.  It was long and warm enough for Phomopsis, and Black Rot to cause infection.  Also, these rains from Saturday probably initiated ascospore release of powdery mildew.  (Powdery mildew does not require water for its infection, but it requires water to release ascopsores from its over-wintering structure.)  The average temperature was low for downy mildew, but between noon to 5 pm Monday, we observed 60-65F while it’s raining.  Thus, it might be accounted for downy mildew as well.

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