UGA Extension Viticulture Blog

Time to Pull out the Big Guns

I think most producers are fully aware that recent rainfall events will increase disease levels in wine grapes.  I am particularly concerned about fruit rots and downy mildew.  In particular, more active materials for downy mildew are needed at this time.  Though the contact materials such as Captan and Mancozeb are good materials, I think it is time to bring in systemic materials as well — at least until we have drier conditions. If I were growing grapes commercially, I would consider use of Ridomil Gold MZ as soon as I could get back into the vineyard; this may be a little earlier trigger than desired, but I think it is warranted with the current conditions in the field.  Ridomil has good kickback activity, and I hope it will take out some infections that may have occurred in the last 24-48 hours.  I would then rotate in the more active materials such as Zampro, Revus (or Revus Top), Ranman + Prophyt, Prophyt + Captan etc. — incorporating the most active materials and using as many fungicide classes as possible for resistance management.  Again, these are downy mildew active materials and you have to cover the rots (Botrytis, black rot, ripe rot, etc.) and powdery mildew as well with other fungicides.  As always, contact your local county agent should you have questions or need additional information.

Downy Mildew Fungicides