What Is Phylloxera, Which Has Destroyed Countless Vineyards Throughout the World?

Phylloxera is a family of sap-sucking aphids that includes the grapevine-devastating root louse Daktulosphaira vitifoliae which is simply referred to as phylloxera in viticulture. (It is still often classified by its old scientific names Phylloxera vastatrix or Phylloxera vitifoliae.) Specifically, it attacks the rootstock to cut off the flow of water and nutrients to the vine.

Phylloxera is native to North America. It is believed to have been introduced into Europe and the Old World winemaking regions in the late 1860s to supplement the needs of growing vineyards and wineries, but spawned a worldwide epidemic, ruthlessly ravaging vineyards from France down to Australia. In France alone, more than 2.5 million hectares (6 million acres) of vines were uprooted. This was on the heels of the ravages of powdery mildew, the leaf disease also known as Oidium caused by Uncinula necator fungus, in the 1850s. (The fungus spreads to grape clusters and causes secondary rot and off-odors described as moldy, earthy and mushroom-like.)

North American grapevines, such as Vitis labrusca, were spared because these had developed natural resistance to phylloxera, however, Vitis vinifera grapevines-used throughout Europe in making world-class wines such as Chardonnay and Cabernet Sauvignon-had not. Interestingly, Chile’s vinifera­-planted vineyards were spared; it is not known why but it is suspected that the louse could not traverse the Andes Mountains from the east because it could not survive high altitudes nor cross the Pacific Ocean from the west.

The cause of the problem was not immediately apparent and was often misdiagnosed. Much research was undertaken to identify root causes (ok, the pun was intended) but this took very long. In the meantime, the louse spread across continents, continuing to inflict damage at a dizzying pace.

Many proposed remedies failed, and failed miserably. There was a glimmer of hope when Baron Paul Thénard, son of French chemist Baron Louis-Jacques Thénard (1777-1857) of hydrogen peroxide fame, applied carbon disulfide, a strong, poisonous and foul-smelling insecticide around the affected vines. The chemical was fairly effective against phylloxera, but it had two shortcomings in addition to being avery expensive treatment making it unsuitable as a long-term solution. First of all, carbon disulfide is very volatile and therefore was required to be applied in large doses. Secondly, it had to be applied annually which weakened vines and in cases of prolonged applications killed vines altogether.

Other chemical warfare was proposed such as potassium xanthate and potassium sulfocarbonate to overcome the first shortcoming of carbon disulfide but again, these treatments were simply too expensive. There was also an attempt to use a very dilute solution of Sarin, an organophosphorus compound chemically known as methylphosphonofluoridic acid 1-methylethyl ester. The solution was applied to the soil around the vine trunk, and although it proved very effective, its use was considered too toxic and dangerous as an ongoing remedy. Sarin is a highly toxic nerve gas once used, for example, as a chemical warfare agent and in the 1995 Tokyo subway attack.

Vineyardists had become desperate, and desperate times called for desperate measures. Some resorted to voodoo-like solutions such as burying toads under the vines to dispel the evil forces but to no avail.

A couple of long-term solutions were finally identified. One solution recommended by Gustave Foëx (1844-1906) Director of the École d’agriculture de Montpellier involved breeding European V. vinifera cultivars with native North American species, however, these “French” hybrid varietals did not produce the same style and quality of wine that the Old World had become accustomed to with V. vinifera varietals. The second solution, now standard practice across the world in planting and replanting vineyards, developed by British-born American entomologist Charles Valentine Riley (1843-1895) and French botanist Jules-Émile Planchon (1823-1888) in the late 1870s, involved grafting V. vinifera vines onto very specific North American rootstocks such as V. riparia; the result is a vinifera-yielding vine on a phylloxera-resistant rootstock.

Today, phylloxera is not as a serious threat, except in those vineyards and winemaking regions that persist on planting ungrafted vinifera grapevines and which have not been attacked yet or those vineyards that had been replanted with vines grafted onto still-vulnerable North American rootstocks as evidenced by the phylloxera strike in California in the late 1980s. Specifically, in Napa and Sonoma counties, vineyards were replanted in the 1960s using a rootstock known as A×R1, or Aramon Rupestris #1, a cross between Aramon, a V. vinifera cultivar, and Rupestris, an American V. rupestris grape species but which have not developed total immunity to phylloxera.

Modern vineyards now have a wide selection of rootstocks known to be highly resistant to phylloxera and which can be adapted to the specific environmental conditions. One example is SO4 or Selection Oppenheim #4, a cross between two native North American species, V. berlandieri and V. riparia cultivars, known to perform well in cool-climate regions, particularly in wet soils.

Considering the cost of ripping vines out and replanting a vineyard, the fact that vines only produce wine-worthy grapes after five years on average, and with its associated revenue losses, it is surprising that history has not been a deterrent to these vineyardists.

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