Phylloxera is a small yellow root feeding aphid. It lives on both European grape vines where is causes disease and also on American vines where it causes little damage.
The pest has a complex life cycle living partly on the leaves of the grape vine and partly in the roots where they cause the damage. The presence of the pest is often first seen when the vine starts to die because of the extent of the damage to the roots.
The pest can be spread by wind or the insects crawling from one plant to the next, but long distance movement of the pest is usually caused by humans transporting infected plant material or soil from vineyard to vineyard perhaps inadvertently in machinery or on boots.
The Extent of the Damage
The pest can kill vines and whole vineyards. It resulted in a reduction in the French wine crop of about 60 percent between 1875 and 1889.
The economic and social dislocation was severe as alternative forms of land use and income had to be found throughout France's Wine Regions. Some French vignerons and merchants moved from Bordeaux to Spain where areas such as the Rioja benefited from their investment and expertise.
The Remedies
Understanding the nature of the problem and devising effective counter measures took several decades.
American vine species have root systems that are resistant to the pest. Thus European varieties of Vitus vinifera can be grafted on to American vine rootstocks. Thus vines can be produced with American vine roots and European vine tops. These grafted vines are resistant to phylloxera but produce top quality fruit for wine making.
Another way of controlling the pest was to crossbreed American and European vines to produce special varieties called French Hybrids. These are resistant to many diseases but wine quality is often poor so the use of these varieties is declining.
The Recovery
By about 1900 the control measures were understood and the recovery was underway. However not all areas were replanted as profitable alternative crops and land uses were found in many regions.
One example in South West France is the Cahors wine region. The region was famous for its 'black wines' based on Malbec during the Nineteenth Century. After the phylloxera devastation Cahors was only a minor producer of wines. Only in the past decade or so has the reputation and production of this region reached its former level.
Phylloxera Today
It could be argued that the pest has been controlled rather than eliminated. Most vineyards throughout the world are now planted with grafted vines, but many are not.
Parts of Australia are phylloxera-free due to a strict quarantine regime but elsewhere resistant rootstocks or hybrid varieties are needed.
