Monday, June 20, 2011

Disease risks from yesterday's rain

We are having a wet Monday.  It started raining on Saturday (luckily, after I finished the most of treatment sprays), but we had a break from rain yesterday morning.   For Winchester, rain started around 8PM Saturday, and the relative humidity was > 90% until 11AM on Saturday.  Thus, it was 15 hours of an estimated leaf wetness period with an average temperature of around 73F.  It was long enough for Phomopsis, black rot, and downy mildew.  Since it was a long event, it was probably an infection event for Botrytis as well.  In addition, we are experiencing nights with high temperature continuously, which promotes downy mildew sporulation.

As I mentioned a few times this year, these isolated thunderstorms are very difficult to predict and measure.  For example, our vineyards start received rain from 4PM on Saturday, but the city of Winchester which is only 6-7 miles away was bone dry.  Plus the rain seemed to come out from nowhere.  I was constantly checking radar while I was spraying...  In anyway, the point here is if you are far away from nearby weather stations, investing on a weather station unit may be a good idea.

FYI: I will be off to a meeting tomorrow until later this week, thus, I may not able to update this blog as often as I wish.  If you need to contact me, email would be the best choice during this week.

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