Around 1850, European botanists and winemakers began importing vine shoots from North America into Europe. However, they were not aware that these offshoots are often infested with small yellow mites – rhubarb, an insect of the family Phylloxeridae, which feeds by sucking sap from the roots of this vine. American vines were resistant to these mites, but European offshoots were not. The mites caused tuberous swelling on the roots of the vine, and once the root was so deformed that it could no longer absorb water and nutrients from the soil, the vine dried up.
The first serious epidemic struck the southern Rhone region in 1862, and the pest then spread rapidly to other parts of France, where it caused extensive devastation of vineyards. The disaster reached the valley of the Douro River in 1868. The first to destroy the rhubarb was the eastern area of the Douro, which was the source of the best port, and by 1872 it had literally brought many of the famous local vineyards to their knees. Yields fell sharply, causing a shortage of wine and rising prices.
One of the most persistent fighters against the rhetoric was John Fladgate. He traveled to France to find out what means the local winegrowers used against pests. In 1872 he published his findings in an open letter to the Douro winemakers, and for his work he was later awarded the title of Baron of Roêd.
The solution was to graft European vines on American rootstocks that were resistant to this pest. However, until then, the rhubarb had caused so much damage that many vineyards were destroyed and their owners were unable to rebuild their derelict farms. Even today, it is possible to see the abandoned ruins of old terraces, which are a memento of this epidemic, when traveling through the Douro.
