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Downy mildew risks

I just want to remind you about the risk of downy mildew remains high this week.

Downy mildew prefer to produce spores under dark and humid conditions.  We experienced a very wet night on the 23rd (no measurable rain, but RH was 100% for 8-9 hours), and then it was followed by a thunderstorm on the 24th (yesterday).  It was a very short storm with ~90 min total wetness duration, which is a minimum time required for downy mildew infection.  In addition, the night time relative humidity have been high for last few days (>80%), and thunderstorms are in the forecast every day of this week.  Moreover, our berries are probably about one to two weeks away from becoming resistant to downy mildew infection (depends on susceptibility of variety and also when it was in bloom). Thus, please make sure to protect your berries from downy mildew as well as black rot.

Picture on the top is a cluster showing downy mildew infection on the tip of a cluster.  The picture below is a close up of another cluster with downy mildew.  I put arrows on berries with downy mildew spore structures.




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