Phylloxera: the parasite that changed wine forever

In June 1863 Prof JO Westwood, a leading entomologist and biologist at Oxford University, took delivery of a vine leaf taken from a greenhouse in Hammersmith. It was covered with a small insect and its eggs. Westwood identified it as an aphid, Phylloxera Vastatrix. He was not aware of its importance, but he was the first in Europe to discover the existence of this tiny parasite that was to change the world of wine forever. At around the same time an unknown disease destroyed several vineyards in the Rhône valley.

Large numbers of plants, including vines, were transported from America to Europe throughout the 19th century. A large greenhouse planted with exotic plants from around the world was an essential part of the wealthy fashionable household. Little thought was given to what diseases these might carry with them. This was to have calamitous consequences for European vine growers. First Oidium, a fungal disease, arrived in Europe in 1847, attacking vines and severely affecting the entire economies of wine-producing regions, followed later by downy mildew in 1878 and then black rot in 1888. But Phylloxera proved the most deadly of all.

The aphid is less than one millimetre long, barely perceptible to the human eye. It attacks the roots of a vine (the only plant affected) feeding on the sap of the roots. It spreads from one vine to another through cracks in the soil, but can also be carried for long distances by wind, farm machinery or on human feet. Affected plants become stunted and eventually die.

The disease quickly spread outwards to include first the Languedoc, then other parts of France. By the end of the century, most of Europe and north Africa had been affected. It is estimated that almost half of all vineyards in France were affected. Many wine regions went into decline, never to recover. Others lost valuable plant material, and changed to more productive lower quality grape varieties. It is hard to imagine how devastating it was for farming communities who were entirely reliant on sales of wine for survival.

At first, many refused to accept that this small parasite could be culpable, believing it to be a symptom rather than a cause. It took a French government inquiry in 1869 to determine that it was indeed responsible. The hunt for a cure took longer than it should, partly due to professional jealousies between French and American researchers. Possible cures included flooding vineyards with water (effective, and still practised in Argentina, but rarely practical) spraying with carbon disulphite (highly flammable and dangerous). Finally, in the 1880s, researchers discovered the only way to prevent infection was to graft resistant American rootstocks onto European scions. Today virtually every vine you see in a vineyard has been treated this way prior to planting.

A few areas managed to stay free of Phylloxera; the aphid cannot survive in very sandy soils, so the great plains of Hungary, Colares in Portugal were immune from attack. Chile, surrounded by the Andes and Pacific Ocean has remained free of Phylloxera and many other plant diseases.

In order to plant a vine, a grower need only stick cuttings directly into the ground. South Australia, by observing strict controls and quarantine has so far remained free. For a time, it seemed as if the dangers posed by Phylloxera had passed. However, several supposedly isolated regions such as Oregon and New Zealand, have discovered to their cost that nowhere is immune. The most expensive recent outbreak occurred in California in the 1980s.

Growers, advised by Davis University, planted many vineyards in California with the AxR1 rootstock, despite warnings from European viticulturists that it did not have sufficient resistance to Phylloxera. The error was to cost dearly; 50,000 acres of vines were destroyed. It is estimated to have cost the industry up to $6 billion to uproot valuable mature vines and replant with vines grafted on to sturdier rootstocks.

Today four wines with a connection to Phylloxera; a wine from disease-free Chile; the Barossa Valley in South Australia has been planted with vines for 150 years and remains free of Phylloxera. Geoff Schrapel of Bethany has old vineyards almost completely planted with ungrafted vines, including most of those used for his delicious Semillon. In Spain, the first disease-free vines to appear were grafted on to to the productive but very neutral Palomino variety. It took 80 years for Ribeiro in Galicia to rediscover its native grapes. And lastly, a Côtes du Rhône, from the first region to suffer from this deadly disease.