THE MOST DEADLY VINE DISEASE
In mid 1800’s, the American wine industry was relatively well established. Researchers conducted experiments to improve yields, taste and growing patterns. Some started cross breeding programmes to improve more than taste, appearance, colour and other desirable characteristics. A few researchers crossed native vitis labrusca, - rotundifolia or – munsoniana family grape varieties, others tried to cross breed grapes varieties belonging to vitis vinifera and native varieties.
A lively exchange of grape vines developed between France and the USA. American researchers and growers were interested in French vines, and in turn French growers wanted to see how well American species would grow on their soils.
In 1865, a shipment of American vine cuttings arrived in the port of Bordeaux and was planted soon after. Two years after the planting, the vines showed atypical galls on the underside of leaves and a year later died. The disease, never encountered before up to that time in Europe devastated French vineyards within a decade, spreading rapidly from region to region, and eventually much of Europe.
Scientists were baffled and could not explain how the disease spread and what caused it. The French government was concerned enough to offer anyone who could solve the problem, 300,000.- French Francs, which would be the equivalent of more than $ 1.5 million today.
Today, we know what causes phylloxera vastatrix, and how to minimize its devastating results.
This terrible disease starts as a green fly measuring 1 – 2 mm with a sophisticated reproduction cycle – in the summer, the winged insect lay two types of eggs on the bark of the vine. The smaller eggs produce male and the larger female offspring. After mating, the female, at the beginning of winter lays one egg under the bark the vine that hatches in the spring to a female phylloxera-causing aphid called the founder. The beetle attaches itself under a young leaf and in turn lays several hundred eggs, which in turn spawn countless generations of gall-dwelling aphids feeding on the leaves.
In autumn, a number of larvae migrate towards the roots and start attacking the roots of the vine causing cellular disruptions that develop to nodes. These nodes cause the total disappearance of the roots, thus causing the vine to die.
In July, to complete the cycle, pupae appear among the root-attacking aphids, which undergo a moulting and become winged insect mentioned first.
These then take advantage of strong winds to spread 30 – 3- kilometres away fro their origin, thus vineyards adjacent to the source of phylloxera may be fully spared from the scourge, and those lying further afield be affected.
Phylloxera vastatrix does not survive in sand and a few small regions on sandy soils have never been affected, but there are only few vineyards on exclusively sandy soils. In any case, sandy soils are not known to yield fine wine grapes.
Two countries have never been affected by phylloxera vastatrix – Cyprus and Chile – due to rigorously enforced import controls of vines.
Grafting vitis vinifera family grapes onto vitis labrusca or rotundifolia or munsoniana rootstock solved the problem to a large extent
Eventually, rootstocks were developed to resist the dreaded disease, but phylloxera still ravages many regions as recently as 1980’s California, forcing thousands of vignerons to replant their vineyards at great expense.
This was caused due to the wrong selection of rootstock.
Article contributed by Hrayr Berberoglu, a Professor Emeritus of Hospitality and Tourism Management specializing in Food and Beverage. Books by H. Berberoglu