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Late season downy mildew and recent rains

I have heard from several growers that they are seeing downy mildew despite the fact that they have not seen much precipitations.  It could happen because of the humidity, especially during the night.  Warm, humid, and dark condition (just like we have been having during the last few weeks) promotes downy mildew pathogen to produce spores.

In addition to these conditions, we had lines of rain storms passed in our areas in the past two days. The length of wetness due to these storms were probably long enough for downy mildew pathogen to cause infection.

So, just a reminder.  If you have seen downy mildew, and you have not applied any protective material (captan, Revus, even phosphorous acid products) in the past 10 days or so, you may want to consider a rescue application of a phosphorous acid product to reduce the risk of infection that might have happened in the past two days of rains.  (Note: If you are considering harvest in a few days, I would wait until harvest.)

If you have not seen much downy mildew, and/or you have protected your vines within the 10 days or so, the risk of downy mildew infection would be low.
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