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Disease risks 11-13 June

Winchester area received quite a bit of precipitation (1.4 inches) from a series of rain event starting from the 11th of June.  We had two wetness periods 14 hours with 69F and 12 hours with 66F.  These were risk events for downy mildew, Phomopsis, black rot, and Botrytis.

We have been rating diseases in our treatment plots for three weeks now.  So far what I see most is downy mildew and a little bit of powdery mildew and black rot.  It makes sense to me to see many downy mildew infections due to recent wetting events and relatively humid nights we had in latter part of May.  I have heard from some growers that they have issues with downy on leaves and clusters.

If you have an issue with downy mildew or concerned about the risk from recent rain event, both Ridomil and Phosphonate (Phosphorous acid) products have a kick-back activity (= able to stop on-going, but not established, infection).  Since resistance against Ridomil products is known to develop among downy mildew pathogens, so, if you have an on-going major downy mildew issue, it is probably better to use a phosphonate + captan (or mancozeb, if the PHI allows you) combination.
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