Mildew, Phylloxera, and the Return of Native Grapes: How Vine Diseases Reshaped Galicia’s Wines

A detailed look at how mildew and phylloxera shaped Galician wine history, leading to major shifts in grape varieties.

In Ribeiro, history is coming full-circle. Last week, the region saw the official approval of new changes to its regulations: non-native grape varieties will be phased out, and native grapes will be promoted. So-called ‘foreign’ varieties Palomino, Garnacha Tintorera, and Tempranillo can no longer be planted or replanted, and Merenzao, Espadeiro, Branco Lexítimo, and Albilla do Avia, which were displaced by Palomino and friends, will be made preferred varieties. 

What’s happening in Ribeiro is the latest step in Galicia’s ongoing march toward quality. But how did Palomino, a grape from Jerez, come to dominate Galician vineyards for so long? The answer lies in a chain of events set in motion nearly two centuries ago, when a wave of vine diseases caused a seismic shift in Galicia’s viticultural landscape that reverberates to this day. To understand what happened, we need to go back in time.

1853 began like any other year in Galician wine country. Life moved to the rhythm of saints’ feast days and the turning of the seasons. In the vineyards, grapes soaked up the summer sun and began to ripen. But that year, something was very wrong. A strange gray pallor began to creep across the vines. The grapes kept growing until their skins split, exposing the flesh beneath. Farmers watched with curiosity, then with horror, as their crop was sucked dry. The creeping sickness devastated everything it touched, leaving the harvest shriveled on the vines.

Only later would they learn its name.

Powdery mildew, or oídio in Spanish, is a fungal disease that thrives in warm, humid climates. It leaves dead spots and a gray-white powdery coating across leaves, shoots, and grape clusters. If the infection is bad enough, it can damage stems and leaves and cause grapes to crack open, leaving them vulnerable to other infections and rot.

Although the disease likely originated in the U.S., it was first detected in 1845 in England, when a gardener spotted grape vines covered in white dust that led to fruit rot. From there, powdery mildew spread fast, and by 1850, it had reached vineyards in most of continental Europe.

Historians disagree on exactly when powdery mildew arrived in Galicia, but they think the fungus came from northern Portugal, traveling up the Miño River valley until it was first spotted in the vineyards of Trives, in modern-day Ribeira Sacra. The initial reaction was surprise and confusion. Contemporary sources described it as “a bad-smelling white powder that kills the vines”; and “a white layer that destroys the crop.” No one, neither rich nor poor, would be spared from the misery and ruin it brought.

Heizer, CC BY-SA 3.0 <http://creativecommons.org/licenses/by-sa/3.0/>, via Wikimedia Commons

It’s difficult to overestimate the damage that powdery mildew inflicted. For nearly a dozen years, small growers whose only income came from their vineyards were dealt crop loss after crop loss. Whole villages were plunged into poverty. Bands of thieves roamed the countryside, and young men enlisted en masse in the army to escape a worse fate at home. 

The disease’s arrival also coincided with years of poor grain harvests, potato blight, and a cholera epidemic; together, they created a perfect storm of poverty and starvation that forced many Galicians to emigrate to the Americas. The demographic shift wasn’t the only lasting impact. After years of failed harvests on the northern coast of the province of Lugo, farmers uprooted their vineyards and replaced them with potatoes and corn. Viticulture in the area completely disappeared. 

A cure was slow in coming as scientists and growers struggled to understand the disease. When the Spanish government held a contest to see who could come up with the best cure, it yielded bizarre proposals that called for using human feces, road dust, or even urine-soaked nails.

The scientific community eventually figured out that treating affected vines with sulfur got rid of powdery mildew. But even with evidence to support sulfur treatments, the practice was slow to be accepted. Some farmers thought sulfur poisoned the grapes, and others just couldn’t afford the supplies to treat their vines. It wasn’t until the early 1860s that sulfur use became more widespread in Galicia, thanks to newspaper editorials, the founding of a “Sulfurizing Society” in Vigo, and government involvement in the province of Ourense, which paid to hand out sulfur-spraying machines in wine-growing villages. By 1865, harvests had almost returned to normal, but powdery mildew still made things difficult. The ongoing threat of fungus required constant vigilance, and the price of sulfur, spraying equipment, and the labor required to apply the treatments raised winemaking costs by about 25%.

Sulfur sprayers returning from the vines - Vida Gallega, June 1917

But powdery mildew was only the beginning. Its arrival marked a before and after in Galicia’s viticultural tradition, and its consequences set the stage for major changes to come.

Downy mildew, powdery mildew’s cousin, sprang up in the late 1880s. Although it damaged vineyards and slimmed down harvests in wet years, downy mildew didn’t have the same devastating effects as powdery mildew did 30 years prior, since by that point farmers knew how to treat fungal diseases. Before long, copper-based sprays of Bordeaux mixture were being used alongside sulfur.

“MILDEW”

“The beginning of May is the opportune time to apply the first sulfur treatment to vineyards; after 20 days the second is applied, and when the berries on the bunches are the size of a pea, the third.”

From the newspaper ‘Galicia Nueva’, May 8, 1909

Around the same time, phylloxera, the vine-killing aphid, crossed into Galicia from Portugal. Galicia wasn’t as hard-hit as other parts of Spain, possibly because of its humid climate and sandy soils. All told, Galicia lost about 10,000 hectares of vines at the height of the crisis, which it had mostly recovered by the 1920s. But phylloxera still had a huge effect on Galicia’s viticultural landscape. The only response to the pest was to graft native vines onto American rootstocks, which were naturally resistant. The replanting process led to a major transformation of Galicia’s vineyards. 

By the late 19th century, Galician growers had endured decades of disease and economic upheaval. Growers were under pressure to turn a profit and start making wine growing financially viable again. Hoping to cut their losses from future waves of diseases, they grafted ‘foreign’ varieties from outside Galicia to American rootstocks. Traditional varieties like Albarello (Brancellao), Mouratón, Godello, and Treixadura were mostly replaced by more productive, disease-resistant grapes like Palomino, Garnacha Tintorera, and, surpisingly enough, Mencía. Garnacha Tintorera (Alicante Bouschet) arrived with Catalan nurserymen in 1889, and Palomino, imported from Jerez around the same time, came to dominate among whites. Apart from these ‘foreign’ grapes, growers also planted new direct-producing hybrids, which could be planted without the need for grafting.

From Valdeorras, the practice of grafting non-native varieties spread across nearly all of Galicia’s wine regions. In Ribeiro, Palomino replaced the classic trio of Treixadura, Torrontés, and Lado that had built Ribeiro’s reputation in medieval Europe. In Ribeira Sacra, Mencía took the place of Albarello, and Valdeorras also saw Godello, its native grape, replaced by Palomino.

By the early 20th century, Galicia’s vineyards had been transformed by choices made in response to disease and economic survival, and most of these new, high-yielding grape varieties remained entrenched well into the late 20th century. In the end, it would take nearly fifty years of mediocre, bulk wine before Galicians finally began to change their ways. Albariño led the charge: the creation of DO Rías Baixas in 1988 sparked a wave of prosperity, and made other regions rethink their approach to quality. In the 1980s, pioneers in Ribeiro began reviving varieties like Treixadura, Sousón, or Ferrón. By the turn of the century, Ribeira Sacra had also joined the movement for quality, embracing Galician grapes, and Valdeorras and Monterrei followed suit. The modern success of these wine regions is largely due to Galicia’s incredible wealth of native grape varieties. Now, Ribeiro’s new regulations represent a long-overdue correction to that legacy. It’s taken generations to get here, but in Ribeiro, and across Galicia, the arc of the viticultural universe is finally bending back toward quality.