Phylloxera - Fighting The "phylloxera Plague"

Fighting The "phylloxera Plague"

In the late 19th century the phylloxera epidemic destroyed most of the vineyards for wine grapes in Europe, most notably in France. Phylloxera was introduced to Europe when avid botanists in Victorian England collected specimens of American vines in the 1850s. Because phylloxera is native to North America, the native grape species there are at least partially resistant. By contrast, the European wine grape Vitis vinifera is very susceptible to the insect. The epidemic devastated vineyards in Britain and then moved to the mainland, destroying most of the European grape growing industry. In 1863, the first vines began to deteriorate inexplicably in the southern Rhône region of France. The problem spread rapidly across the continent. In France alone, total wine production fell from 84.5 million hectolitres in 1875 to only 23.4 million hectolitres in 1889. Some estimates hold that between two-thirds and nine-tenths of all European vineyards were destroyed.

In France, one of the desperate measures of grape growers was to bury a live toad under each vine to draw out the "poison". Areas with soils composed principally of sand or schist were spared, and the spread was slowed in dry climates, but gradually the aphid spread across the continent. A significant amount of research was devoted to finding a solution to the phylloxera problem, and two major solutions gradually emerged: grafting cuttings onto resistant rootstocks and hybridization.

Use of a resistant, or tolerant, rootstock, developed by Charles Valentine Riley in collaboration with J. E. Planchon and promoted by T. V. Munson, involved grafting a Vitis vinifera scion onto the roots of a resistant Vitis aestivalis or other American native species. This is the preferred method today, because the rootstock does not interfere with the development of the wine grapes, and it furthermore allows the customization of the rootstock to soil and weather conditions, as well as desired vigor. Unfortunately not all rootstocks are equally resistant. Between the 1960s and the 1980s in California, many growers used a rootstock called AxR1. Even though it had already failed in many parts of the world by the early twentieth century, it was thought to be resistant by growers in California. Although phylloxera initially did not feed heavily on AxR1 roots, within twenty years, mutation and selective pressures within the phylloxera population began to overcome this rootstock, resulting in the eventual failure of most vineyards planted on AxR1. The replanting of afflicted vineyards continues today. Many have suggested that this failure was predictable, as one parent of AxR1 is in fact a susceptible V. vinifera cultivar. But the transmission of phylloxera tolerance is more complex, as is demonstrated by the continued success of 41B, an F1 hybrid of Vitis berlandieri and Vitis vinifera. The full story of the planting of AxR1 in California, its recommendation, the warnings, financial consequences, and subsequent recriminations remains to be told. Modern phylloxera infestation also occurs when wineries are in need of fruit immediately, and choose to plant ungrafted vines rather than wait for grafted vines to be available.

The use of resistant American rootstock to guard against phylloxera also brought about a debate that remains unsettled to this day: whether self-rooted vines produce better wine than those that are grafted. Of course, the argument is essentially irrelevant wherever phylloxera exists. Had American rootstock not been available and used, there would be no V. vinifera wine industry in Europe or most places other than Chile, Washington State, and most of Australia. Cyprus avoided the phylloxera plague, and thus its wine stock has not been grafted for phylloxera resistant purposes.

By the end of the 19th Century, hybridization became a popular avenue of research for stopping the phylloxera louse. Hybridization is the breeding of Vitis vinifera with resistant species. Most native American grapes are naturally phylloxera resistant (Vitis aestivalis, rupestris, and riparia are particularly so, while Vitis labrusca has a somewhat weak resistance to it) but have aromas that are off-putting to palates accustomed to European grapes. The intent of the cross was to generate a hybrid vine that was resistant to phylloxera but produced wine that did not taste like the American grape. Ironically, the hybrids tend not to be especially resistant to phylloxera, although they are much more hardy with respect to climate and other vine diseases. The new hybrid varieties have never gained the popularity of the traditional ones. In the EU they are generally banned or at least strongly discouraged from use in quality wine, although they are still in widespread use in much of North America, such as Missouri, Ontario, and upstate New York, where they yield commercially acceptable wines.

The only European grape that is natively resistant to phylloxera is the Assyrtiko grape which grows on the volcanic island of Santorini, Greece, although it is not clear whether the resistance is due to the rootstock itself or the volcanic ash on which it grows.

To escape the threat of phylloxera, wines have been produced since 1979 on the sandy beaches of Provence’s Bouches-du-Rhône, which extends from the Gard Coast to the waterfront village of Saintes Maries de la Mer. The sand, sun and wind in this area has been a major deterrent to phylloxera. The wine produced here is called "Vins des Sables" or "wine of the sand".

In the same department, where the canal irrigation system built by the Romans still partly persists to this day, winter flooding is also practiced where possible, for instance south of the city of Tarascon. Flooding the vineyards for 50 days kills all the nymphs that overwinter in the roots or the bark at the bottom of the plant.