Friday, October 23, 2015

The Story of Phylloxera: How a Tiny Insect Changed the Global Wine Industry Forever

In the late 1700s Thomas Jefferson, a connoisseur of French wine, attempted to grow European grape vines at his home in Virginia.  All of his imported European vines died, and he never knew why.  A century later, the whole world was introduced to the vine-killing culprit.

The tiny insect Daktulosphaira vitifoliae in the family Phylloxeridae (phylloxera for short) comes from eastern North America.  This almost microscopic, pale yellow insect, related to aphids, feeds on a grape vine’s roots and leaves.  Grape vines native to the same areas (such as Vitis aestivalis, rupestris, riparia, and labrusca) have developed resistance to this pest, but European grape vines (Vitis vinifera) have no resistance.

The Nymph Form of Phylloxera Feeds on Vine Roots

For many years, American grape vines were brought to Europe as botanical specimens. Phylloxera insects that hitched a ride on the vines went unnoticed and died during the weeks it took for sailing ships to cross the Atlantic.  All that changed in the 1850s when steam ships reduced trans-Atlantic crossing time to only ten days, a short enough time that the insects could survive the journey. Thus, phylloxera arrived and began its slow march across Europe.

The problem was first noticed in southern France in 1863, when leaves withered, shoots were weak, and grapes did not ripen.  Symptoms worsened for a few years until the vines died.  Pulling up the dead vines revealed that their root systems had nearly disappeared. Once phylloxera was identified as the problem, a cure was difficult to find.  Because phylloxera live on both roots and leaves, have a complex life cycle, and are highly adaptable, they are difficult to kill.  Common pesticides either weren’t effective or couldn’t reach the roots of the plant which were being eaten away.  New techniques developed for combatting phylloxera were ineffective, impractical, or nearly as destructive as phylloxera itself.

Phylloxera on a Grape Vine

The phylloxera epidemic impacted France the most, as it was the largest producer, consumer, and exporter of wine at the time.  But phylloxera eventually spread to all of Europe.  Between 60% and 90% of all European vineyards were destroyed during this time.  In France, wine production fell 75% between 1875 and 1889.  Ultimately the entire global wine industry was threatened.

The resulting shortage of wine affected many countries and wine markets.  At first, the decrease in supply of French wine increased the demand for wine from countries not yet affected by phylloxera, such as Spain and Italy, until phylloxera reached their vineyards as well.  Demand for Chilean wine increased, since Chile’s vineyards were planted primarily with imported European vines.  The shortage also created a market for terrible wine, made from imported raisins, or flavored with the used must (seeds and skins) left over from previous vintages and combined with beet sugar to produce alcohol.  It also inspired a flood of fake wine, poor quality wines labeled and sold fraudulently under the names of famous chateaux.  The wine shortage in France also led to an increase in the popularity of absinthe, a hugely influential beverage of the early 20th century which requires an article of its own.  In Britain, the Scotch industry promoted itself as a replacement beverage and many British wine drinkers switched.

In response to phylloxera, the French could not simply pull up their European vines and replant their vineyards with phylloxera-resistant American vines, because the American varieties produce undesirable (“foxy”) wine flavors.  By 1870 American and French scientists had created American-French hybrid vines which they hoped might resist the pest but still produce good wine.  The resulting hybrids had a weak resistance to phylloxera, but were hardy and produced reasonably good wine.  (Some of them are still grown in the United States today.)

The best option turned out to be grafting.  Attaching a European vine to American roots gives the European vine resistance to phylloxera.  (The rootstock that worked the best came from Texas!) Since the genes for the grapes are in the scion (stem), the grapes are unaffected.  Implementing this solution was another challenge, since France had around 11 billion vines in need of phylloxera protection.  Grafting was not accepted overnight.  It took nine years to prove its efficacy and for the French authorities to approve its widespread use. The finest vineyards were reluctant to graft and replant, since the identity of their wines was closely linked to the old, traditional vines.  These producers fought to chemically treat and save each vine, while the smaller, less recognized producers pulled up their vines, grafted, and replanted all at once.  Some producers smuggled American vines into France illegally and made wine directly from the grapes, despite the less desirable flavor and regulations against this practice. Unlike France, countries affected by phylloxera in later years had the benefit of knowing to graft their vines as soon as the problem appeared.

A European Scion Grafted onto American Rootstock

A few wine regions in the world escaped phylloxera completely.  Soils dominated by sand and schist impede the progress of the insect, as do dry climates.  Chile, bordered by an ocean to the west, mountains to the east, desert to the north, and the Antarctic to the south, has never been invaded by phylloxera, though to this day any imported vines must be carefully checked and quarantined.  A quarantine is in effect in South Australia, because it hasn’t yet experienced phylloxera, though neighboring Victoria has.  The island of Cyprus, the Spanish region of Jumilla, and a handful of vineyards in France, Portugal, New Zealand, Greece, England, and the pacific northwest of the United States have also escaped this costly pest so far.

However, the danger is still present, as evidenced by the disaster that struck the California wine industry in the 1980s and 1990s.  Many vines had been grafted onto rootstock beneficial for production, but with a low resistance to phylloxera, under the assumption that the insect was not present in the area.  Phylloxera struck, killing many vines, causing many more to be replaced, and ultimately costing the California wine industry more than one billion dollars.

Ironically, a phylloxera infestation can bring about positive changes.  The need to dig up and replant vines provides an opportunity to change grape varieties to better suit a particular vineyard, or adjust the density of the plantings.   Grafting itself can be helpful, because the grower can choose a type of rootstock which thrives in the specific soil and weather conditions of the vineyard.

Does grafting affect the taste of the wine?  Opinions differ.  While some top wine critics say they cannot taste the difference between grafted and ungrafted grapes, others claim that the ungrafted and pre-phylloxera vines make better tasting wine.  One possible reason for any flavor difference might be that ungrafted vines may produce lower yields.

Phylloxera is the most destructive crop epidemic of all time, and it changed the wine industry forever. Today 85% of the wine grapes in the world come from European vines grafted onto American rootstock.  Despite the enormous costs, phylloxera acted as a catalyst for a huge growth in grape vine knowledge, the chance to improve viticultural practices in established vineyards, a more resilient global wine industry, and in many cases better wine.

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