All About The Wine Pest Phylloxera

Grape growers have always dealt with pests and disease throughout history, but you might be surprised to learn that due to one near-microscopic little louse, about 90% of fine wine grape vines growing today are grown on American roots. In fact, this tiny little critter called the Phylloxera louse is responsible for killing approximately 40% of the legendary vineyards of France during the height of the “Great French Wine Blight”.

The Phylloxera Louse and its Origin

Phylloxera is a louse or aphid native to the Americas that preys on grapevines much like all aphids. The bug pierces the roots of the grape vines to drink their sugary sap, injecting a venomous toxin into the roots, hindering the ability of the vine to absorb water and nutrients. Eventually, the vine ceases to produce fruit and dies a slow death, and must be replanted. Grape vines take on average a minimum of 4 years to mature before their fruit is deemed worthy of wine production. Vines can live as long as 100+ years when conditions are right, so losing an esteemed old vine to a pest like Phylloxera is a hard blow for any wine grape grower. 

Traditionally speaking, most fine wine is made of one single genus-species, Vitis vinifera. This breed of grape has many cultivars or subspecies to which growers have assigned names such as Chardonnay, Pinot Noir, and more. Vitis vinifera is native to Europe, and was introduced to the New World along with the Spanish missions in the 16th and 17th centuries. These early rugged grapevines, called Mission Grapes, were thick-skinned and accustomed to arid environments in Spain and so grew decently well in the dry, high plains of California. Growers and farmers proceeded onward, blissfully ignorant of the microscopic monster that lay just below the surface and was preying on their vines. 

The Great French Wine Blight

Over the next century, American scientists discovered new species and varieties of grape vines in the Americas such as Niagara, Concord and Norton. In the mid-1800s, curious botanists and horticulturalists were very keen to learn how these new, unique species would perform and propagate across the pond. These recently discovered American breeds had evolved in the presence of Phylloxera and as such had created natural defenses and near-immunity to the louse, but unbeknownst to these botanists, the vines still harbored the microscopic bugs and their larvae as they made their journey to Europe. Once planted in the moist, clay soil, Phylloxera began to spread and ravage its way through France, infecting and killing vines in some of the most prestigious vineyards in all of Europe. Called “The Great French Wine Blight,” over 40% of France’s vineyards were destroyed in a period from the late 1850s to the early 1870s. 

As Phylloxera decimated the vineyards of Europe, many brilliant horticulturists and scientists across the globe worked feverishly around the clock to discover a solution to this microscopic villain. Initial findings showed that there was indeed a louse to blame, but the consensus was out if the bug caused damage to the leaves or the roots of the vine, and even if it was different in any way than the well-known French grape louse. Scientists continued to try their theories, from pesticides to placing toads under vines, eventually learning by experimentation that it appeared American grapevine roots were not nearly as susceptible to the pest. The end was finally in sight when a team of botanists reached out to one unsuspecting university botanist named Thomas Volney Munson from the small town of Denison, Texas, and ventured to collect rootstock specimens from his lab vineyard of American grape varieties. They proceeded to graft the traditional European varieties onto these resistant American rootstock, which seemingly put an end to the devastation and maintained the quality of the fine European grape species.

Phylloxera in Modern Times

Today, there is still no true cure for Phylloxera, and it is now present essentially worldwide, excepting certain unique biospheres where the climatic conditions do not allow it to survive, such as high altitude deserts and acidic volcanic soils. As such, cultivating Vitis vinifera vines ungrafted on their own native rootstock is quite a rarity indeed. Some vineyards still maintain ungrafted or own-rooted vines; a fact they are more than proud to tout, and much is written from those who had the opportunity to taste the prestigious French wines from vines growing on their own roots before the Great French Wine Blight occurred. In recent decades, much experimentation and dedication has gone into cultivating a superior form of American rootstock that is even more impervious to the Phylloxera louse. Agriculture schools such as UC Davis developed specific cultivars of rootstock, with varying degrees of susceptibility to Phylloxera such as the once-popular AxR-1 and in recent years the GRN-1 and GRN-3. Over the years, growers have learned that each new rootstock comes with its own particular challenges and susceptibility, making cultivation on grafted vines an incomplete and evolving science. 

We may never know what the wine world would have looked like if Phylloxera had not spread around the globe, but one thing remains true-- the wine world is forever changed due to this one, infinitesimally small bug.