Long before the devastation of phylloxera in Bordeaux: the crisis and its consequences, the Bordeaux vineyard was struck, in the mid-19th century, by a major and lesser-known sanitary crisis: powdery mildew (oidium). This fungal disease, caused by Erysiphe necator originating from North America, profoundly reshaped the region's ampelographic landscape. This period acted as a true catalyst for change in Bordeaux viticulture, as highlighted in “Bordeaux, une histoire de cépages” by Jean-Baptiste Duquesne.

The emergence of a new fungal threat

First appearing in Gironde around 1851–1853, powdery mildew—recognisable by its powdery white coating on leaves and bunches—spread at lightning speed. Winegrowers, unaccustomed to treating their vines, found themselves helpless against this scourge which caused berries to split, irreparably compromising both yields and quality. Losses were colossal, reaching up to 80% of production in some cases, causing outright panic across the vineyards (vine diseases). M. de Kercado and M. des Moulins, members of the Commission générale de la maladie de la vigne, were particularly concerned by certain growths or scabs observed on the vine trunks.

The fight takes shape and its impact on grape varieties

The providential solution was discovered in the use of sulphur, applied by dusting. However, this innovation came at a cost, requiring equipment and labour, thereby creating an economic divide across the vineyard. Only the wealthiest estates could afford these regular treatments. This marked a turning point in vineyard management practices, establishing sulphur as a key element of vine protection (the role of sulphur).

At the same time, winegrowers observed that susceptibility to powdery mildew varied greatly between grape varieties. Some, such as Crouchen or Prueras among white varieties, and even Merlot to a lesser extent, proved particularly vulnerable. Others, conversely, showed a more advantageous relative resistance, such as Sémillon, Folle Blanche (or Enrageat), or Malbec. This disparity in the face of the disease led to a progressive and major overhaul of the varietal mix, contributing to the simplification of Bordeaux’s grape palette (reasons that led to the simplification of the varietal mix in the vineyard).

A new ampelographic landscape

In less prosperous areas or for everyday drinking wines, winegrowers favoured replanting more resistant and high-yielding varieties, often at the expense of aromatic finesse. Such was the case with Folle Blanche in the Entre-Deux-Mers or Malbec on the Right Bank, supplanting more delicate varieties. The Grand Cru Classé estates, possessing the means to sulphur their vines methodically, were able to maintain nobler yet more sensitive varieties such as Cabernet Sauvignon.

The resonance of this crisis today at Château Cazebonne

The powdery mildew crisis was therefore a primary driver of standardisation and reduced ampelographic diversity in Bordeaux, well before the devastation of phylloxera and the regulatory constraints of the AOCs. It marked a decisive turning point in the history of the region's grape varieties. At Château Cazebonne, our commitment to replanting ancient grape varieties aims to reclaim this lost diversity. We are studying how these once-forgotten varieties, including those that suffered from powdery mildew, can be cultivated today using environmentally friendly methods.

To deepen your knowledge of Bordeaux's viticultural history and its grape varieties, we invite you to receive the digital edition of the book "Bordeaux, une histoire de cépages" by Jean-Baptiste Duquesne, published by Éditions BBD, by visiting get the digital edition. Then, test your knowledge of these fascinating historical chapters with our wine quizzes. This adventure is made possible thanks to the support of the many enthusiasts who have purchased our wines online and believe in our approach to preserving Bordeaux's ampelographic heritage.