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Disease risk events from last two weeks and quick reminders

Here are snapshots from the NEWA risk models from the past two weeks.

Floyd: no black rot or downy mildew infection events
Afton: black rot and downy mildew infection event on 7/1-2.
Winchester: downy mildew infection event on 7/8

Looks like we are having relatively dry conditions. Depends on where you are and which cultivar you grow, you may not need to worry too much about downy mildew or black rot for a while. Also, most of our vines are done with the critical period of cluster susceptibility to black rot, downy mildew, and powdery mildew.





What I would keep eye on will be powder mildew, since the pathogen does not require water for infection. Sulfur is a good material, and you can add powdery mildew materials, such as Quitec, Vivando, Torino, DMI, and SDHI to provide extra protection. When you spray a sulfur product, make sure the sprayed material will be dried up before temperature gets above mid-90F. If the leaf surface is wet with sulfur when the temperature gets high, it can cause phytotoxicity. Since powdery mildew thrives under shaded conditions, canopy management is important too (as you can see on the pictures above).

You may need to consider an application against Botrytis and ripe rot at bunch closure, which is good timing for you to make sure your spray materials will be delivered to inside of the cluster structure. For the list of materials against powdery mildew, Botrytis, and ripe rot, please refer to my previous presentation slide.


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