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Another reminder on downy mildew

It looks like many of us received some rain in the past few days, and we may see another rain toward the end of this week.

Here are recent downy mildew infection risks based on the NEWA's DMCast.

Floyd, VA (note: the temperature sensor has been fixed recently, and that's why it shows records from mid-June.)


Crozet, VA (note: the precipitation sensor has been fixed recently! We really appreciate the willingness and commitment of the personal weather station owners!)


Winchester, VA

Protective materials for downy mildew are Ziram (FRAC M3), Captan (FRAC M4), Fixed copper (FRAC M1), Revus or Forum (FRAC 40), or Zampro (FRAC 40 + 45), or Ranman (FRAC 21)).

  • There are increasing cases of Revus resistant downy mildew isolates in VA. Plus, resistance to Ranman is known among downy mildew pathogens of other crops. Make sure to spray before the rain and rotate the FRAC codes!
Materials with kick-back activities are Phosphorous acids (Prophyt, Phostrol, etc, FRAC P07), and Ridomil products (FRAC 4, make sure to check the PHI since Gold MZ has a 66-day PHI). If you think your previous application was washed off before the recent rain events, it is probably a good idea to add a Phos acid to your tank mix. 
  • It is a good idea to tank-mix a phosphorous acid and a protective material, especially your cultivar(s) is sensitive to downy mildew.
  • Please do not mix a phosphorous acid product with copper. Our results show a high probability of causing phytotoxicity.
That's it for today. I wish you all a happy July 4th!!

[note: Since Google dropped the blog subscription system, I have been working on alternatives. If you were a subscriber, you may receive an email from ext.grapepathology.org address.]






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