Mâconnais 2025: Understanding an Exceptional Mildew Crisis
Why southern Burgundy faced rare mildew losses while much of France was spared.
In 2025, the vineyards of the Mâconnais found themselves in an unusual and troubling position. While most French wine regions navigated the season without major sanitary disruption, southern Burgundy—alongside the neighboring Beaujolais—suffered severe losses due to downy mildew. The episode was significant enough to prompt a structured response from the Chambre d’agriculture de Saône-et-Loire, which launched a dedicated action plan inspired by strategies developed in the Bordelais.
The 2025 campaign now stands as a case study in how local climatic sequences, rather than national trends, can dictate outcomes in the vineyard.
A Local Climate Working Against the Vine
The explanation begins with rainfall, but not rainfall alone. In the most affected communes—Lugny, Leynes, Chaintré, Davayé, Prissé, Péronne, Vinzelles, and Saint-Maurice-de-Satonnay—precipitation exceeded long-term averages by a wide margin. More decisive than the totals, however, was the timing.
Heavy rain in mid-April coincided with early leaf emergence, precisely when overwintering mildew spores were reaching maturity. This created an early window of contamination rarely seen with such intensity in the region. The situation deteriorated further in May, when a sharp rise in temperatures accelerated vegetative growth, followed almost immediately by renewed rainfall during flowering. Protection became technically complex, as rapid shoot growth repeatedly outpaced spray coverage.
The result was an explosive epidemiological dynamic. Symptoms appeared unusually early, first on foliage and shortly thereafter on bunches, leaving little margin for corrective action.
When Technique Makes the Difference
Yet climate alone does not explain the scale of damage. Within the same micro-zones, outcomes varied sharply from one estate to another. This disparity drew the attention of technical teams, who examined treatment calendars, product choices, and application methods in detail.
The initial intervention proved decisive. Early positioning of the first treatment, aligned with the earliest health alerts, consistently delivered better results. Delays of even a few days reduced protection efficiency under such pressure. Product strategy also played a role, particularly at the beginning of the cycle, though no single formulation guaranteed success. Application quality, canopy management, and renewal timing relative to rainfall were often more influential than the nominal strength of the program.
One operational detail emerged as critical: trimming had to be completed before spraying. Estates that reversed this sequence effectively removed treated tissue and exposed unprotected growth, reminding practitioners that technical coherence matters as much as chemical choice.
Beyond the Number of Treatments
Contrary to common assumptions, the total number of spray passes did not determine success. Some heavily treated vineyards still failed, while others with comparable or even lighter programs limited damage through precise timing. Equipment choices showed tendencies rather than certainties, and green work, aside from trimming order, played a secondary role.
This reinforces a broader lesson increasingly familiar to experienced winegrowers: under extreme disease pressure, anticipation and execution outweigh repetition.
Rethinking Old Assumptions
The 2025 crisis also revived debate around winter sanitation and inoculum reduction. While intuitively appealing, this strategy offers limited protection against an epidemic disease driven by favorable in-season conditions. Reducing primary inoculum may delay onset, but it cannot prevent rapid escalation once climatic thresholds are crossed. The real benefit lies in gaining time—sometimes only days—to navigate a sensitive phenological stage.
A Glimpse of the Future
Beyond technical conclusions, the season exposed a deeper unease within the profession. For younger winegrowers in particular, the convergence of climatic instability and regulatory constraint raises questions about economic and human sustainability. The response proposed by local authorities emphasizes adaptability: sector-based monitoring, equipment readiness, and the abandonment of standardized programs in favor of vintage-specific strategies.
The discussions held in 2026 at the Cité des Climats de Mâcon reflected this shift in mindset. The 2025 mildew crisis in the Mâconnais was not an accident, nor an anomaly easily dismissed. It was a reminder that precision, vigilance, and local intelligence are becoming central to viticulture in a changing climate—especially in regions where tradition and terroir leave little room for error.