In the time of Covid-19 18 March 2020

As we batten down and plan survival-in-isolation strategies with Covid-19 now a reality in South Africa, I thought it would be interesting to look at the relatively recent history of wine industry pandemics. There are two useful comparisons – the first the great vineyard catastrophe of the 19th century brought about the arrival of the phylloxera in Europe. The second is South Africa’s perennial problem of leaf-roll virus.

Phylloxera is an aphid endemic to the United States. It dines off the roots of grape vines (mainly vitis vinifera), the source of most of the world’s table wines. Phylloxera made its transatlantic voyage in the mid-19th century, probably in the soil of plants (including vitis lambrusca vines) imported to England from America. It turned out to be an enthusiastic traveller. In this it was unwittingly assisted by botanists keen to share exotic plant discoveries with friends and colleagues across the Channel. By 1863 vineyards in the Rhone valley – 1100 km distant from Kew Gardens – were seen to be dying from a seemingly inexplicable contagion.

Over the next 25 years it spread across France and much of Europe. In 1889 wine production in France was 25% of what it had been fifteen years earlier. Phylloxera was first identified in South Africa in a garden in Mowbray in Cape Town in 1886. It made equally impressive progress here. By then it was also in Australia, though given the distances between wine-producing regions, its progress was slower. The Australians implemented rigorous protocols aimed at containment, wherever control was possible. Today South Australia remains phylloxera-free and as a result has some of the oldest and most venerable vineyards in the world. The Grandfather’s Block on the Henschke estate, which was planted in 1860, still contributes fruit to the cellar’s Hill of Grace Shiraz.

For a time Australia was able to limit the spread of phylloxera. While parts of Victoria succumbed before the protocols were put in place, others – such as the Yarra Valley an hour’s drive north of Melbourne – survived without any evidence of the aphid for more than a century. Then, less than twenty years ago, one of the big multinationals moved some of its farming equipment from a contaminated region to the Yarra (breaching the containment regulations): by 2006 it was detected there and the Maroondah Phylloxera Infested Zone established. Since then the zone has been extended at least seven times – illustrating the limitations of containment as a strategy once the bug has arrived in a region carpeted with vineyards.

South Africa’s major vineyard problem is leaf-roll virus, an incurable infection which attacks the leaves of the vines, turning them a lovely russet colour early in summer. Without chlorophyl the plant battles to ripen its grapes. By late summer, the fruit is in an arrested state of development: the tannins are still hard, acidity plummets and the berries begin shrivelling. Wine made from the fruit of virused vines usually shows “stress” characters and is generally unsuitable for premium wines.

The leaf-roll virus problem used to be much worse, but the protocols established by the University of Pretoria’s Professor Gerhard Pietersen (initially for growers in New Zealand with the same problem) have played a significant role in containing the spread. Where individual vines manifest signs of virus they are removed, those in their immediate vicinity are marked and if necessary grubbed up. As a result, for the cost of the loss of a few vines, transmission (either via mealy bug or contaminated secateurs) is arrested. This means that most of the vineyard survives and can be nurtured towards a state of real maturity and the R300k per hectare replanting cost deferred. More importantly, since the best old vines produce the most intense and complex fruit, there’s real benefit in terms of wine quality. Clearly, with virus, containment works and is also cost-effective – unlike phylloxera where it only takes a clod of soil in the tread of a tyre to bring about the next deluge.

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