Seed Treatment Against Sunflower Downy Mildew: 120-Day Derogation for SCENIC GOLD
Seed Treatment Against Sunflower Downy Mildew: 120-Day Derogation for SCENIC GOLD
Context
The fight against sunflower downy mildew (Plasmopara halstedii) is an integrated management strategy where agronomic practices play an essential role:
- Crop rotation of more than one year out of two is strongly recommended.
- Inter-cropping management.
The second key lever is genetic resistance, which is not always sufficient within the current varietal offerings. This is particularly true in the case of resistance to downy mildew race 714 in some varieties when resistance relies on a single gene, especially if that gene is overcome (as race 714 circumvents the Pl8 resistance gene, for example).
In such situations, an effective seed treatment against downy mildew is strongly recommended. These cases are outlined in the joint note by Terres Inovia, GEVES, and INRAE (2024 Note).
History
Since 2021, the seed treatment LUMISENA / PLENARIS (oxathiapiprolin) has fulfilled this role. Initially, it was combined with APRON XL (withdrawn for field use in 2021) and later with RESSIVI, two other modes of action effective against downy mildew.
The combination of two different modes of action is the cornerstone of sustainable fungicide management for this type of disease. The resistance of downy mildew to metalaxyl-M (APRON XL) is a well-documented example. Resistance emerged in the mid-1990s, just a few years after its initial use.
Oxathiapiprolin (LUMISENA / PLENARIS) is potentially at risk of resistance development because its mode of action is also single-site (oxathiapiprolin is classified under FRAC group 49 by the Fungicide Resistance Action Committee). This means that a single spontaneous mutation in the fungicide's target site could render downy mildew resistant.
If seed treatment is used successively in the same field without any additional management measures, resistance is selected and becomes widespread. While resistance to oxathiapiprolin has not yet been identified in sunflower, it has been observed in grapevine and potato, indicating a significant risk.
Since the planned withdrawal of RESSIVI (EU approval withdrawn in June 2024 – REG 1107/2009), LUMISENA / PLENARIS has been used alone.
Derogation
To ensure sustainable management of downy mildew (without resistance), particularly when genetic resistance is insufficient (only one effective gene or no effective gene), Terres Inovia submitted a request for a 120-day derogation (Article 53 – REG 1007/2009) for the SCENIC GOLD seed treatment to be combined with LUMISENA / PLENARIS.
The derogation, granted by the French Ministry of Agriculture, Food Sovereignty, and Forestry on November 12, 2024, will allow seed treatments with SCENIC GOLD for sowing from March 1, 2025, to June 29, 2025.
SCENIC GOLD is a seed treatment fungicide by Bayer CropScience, containing fluopicolide (pyridinylmethyl-benzamides – FRAC group 43) at 200 g/L and fluoxastrobin (strobilurin – FRAC group 11) at 150 g/L. Both substances are effective against sunflower downy mildew, as demonstrated by Terres Inovia’s trials.
SCENIC GOLD is also effective against seedling damping-off diseases (caused by Fusarium, Pythium, and Botrytis), offering a potential alternative to CELEST.