In preparation for Hurricane Delta

Hurricane Delta seems to impact our regions, starting Saturday (10/10), and rain may last until Tuesday (10/13) or so. Depends on your location and cultivar selection, you may have some grapes that may need more time before harvest. (A link to Hurricane Delta tracker from – will play a video.)

The target diseases right now are late-season fruit rots (Botrytis, ripe rot, bitter rot, etc.) and downy mildew (on leaves).

The links here are the presentation slides from the last viticulture meeting that covers some of the diseases mentioned above and a list of short PHI materials for Botrytis, powdery mildew, and downy mildew, which may help you decide what to do.

If you decided to wait until the storm is over, there are several materials with a very short PHI that you may want to consider, such as Oso/Ph-D or Elevate for Botrytis and a phosphorous acid (Prohyt, Phostol, etc.) or Lifeguard for downy mildew. FYI: when we tested in the field, Oso plus Double Nickel combination worked well against sour rot, and Switch works well against Botrytis and has a suppressive effect against sour rot (PHI = 7 days).

It may not be a good idea to spray captan, sulfur, and copper near harvest due to their potential negative impacts on the fermentation and wine quality. (but as usual, please assess your situations (vineyards, winery, economics, etc.) carefully.)

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