Sunday, August 8, 2010

Disease risks of last week

Winchester area experienced much needed rain events during last week (8/3 to 8/4 and 8/5).  [note: I'm at a meeting right now and I didn't have a time to update the information before I took off to this meeting.]

Light rains went through during evening of 8/3 and then after midnight/early morning (1:20AM) in  (8/4), then a thunderstorm hit in the afternoon.  The first series of rains were short and low in the amount of precipitation, but since it occurred at night, the relative humidity stayed high (>90%) until 9:30 AM or so, resulting in 8 hour of wetness with an average temperature of 78F.  The thunderstorm was not as big as we hoped for (it became more severe and brought more rain after it passed our area), and things dried up within an hour.  The midnight rain event was warm and long enough for Downy mildew and Botrytis development.

Then another series of thunderstorm hit our area on 8/5.  As with any thunderstorms, it was sporadic and some area received more than others even within the same area.  It started around 1PM and several lines of rain passed until around 6PM, dropping ~0.38 inches.  However, the air was dry in between rains and after the rain, thus, it probably only accounted as Downy mildew event.

Also we are having several humid nights during last 10 days or so.  This conditions favors spore production of downy mildew.  As I noted in the previous post, many of us had such a dry weather this summer and downy may not be the primary concern; however, we are having weather events that favors infection and spore production.  Please scout for downy by looking at young leaves and if needed, react to the situation.

As noted earlier, I'm at a meeting until next Wednesday (8/11).  The best way to contact me is email.  We don't have rain in the forecast until Thursday.

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