With the restriction on mancozeb in grape to one prebloom application, use of Ridomil Gold-MZ was also restricted and use plummeted so the product was discontinued writes Wendy McFadden-Smith, tender fruit and grape IPM specialist, OMAFA. 

The Pest Management Regulatory Agency (PMRA) has resurrected this very useful tool for grape with the approval of Ridomil Gold.  This systemic fungicide is the gold standard for downy mildew control in grapes.  It has post-infection and protectant activity and translocates to newly developing leaves and to fruit.  The downside is that it is very prone to rapid resistance development.  It is limited to one application per season, either pre- or post-bloom, and should be used before infection rather than as an eradicant to further reduce the risk of resistance. The label states RIDOMIL GOLD 480SL must be applied in a tank mix that includes a non-Group 4 fungicide with efficacy against downy mildew.  This is critical to prevent resistance.  Copper fungicides would be a great tank mix partner.  Syngenta is currently testing some tank mixes for compatibility.

Note: the preharvest interval is 50 days so make sure you use the product early enough in the season.

Here is the link to the label:  Ridomil Gold 480 SL

Source:   ONFruit May 15, 2025 newsletter