WINE: Winning War On Leaf Roll Virus
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VERGELEGEN wine estate in Somerset West is pioneering a multi-million rand, long term strategy to free itself from the grip of leaf roll virus, a pandemic that costs the wine industry billions and undermines its international standing.
The disease is specific to grape vines and affects most of the vineyards in the country. While not a serious a problem in 80% of white grape varieties, it is much more apparent in reds, where it affects the quality and volume of the harvest. Eventually the vines become uneconomical and must be uprooted.
Vergelegen’s wine maker Andre van Rensburg has been working with the University of Pretoria’s Gerhard Pietersen, a world-renowned expert on leaf roll. Together they have implemented a strategy to get rid of infected vines and keep the replanted vineyards virus-free. It’s a war of attrition that to date has seen 120 hectares of vineyards uprooted and replanted at a cost of R75 000/hectare just to prepare the ground.
The new vines are screened annually for the virus using a test Professor Pietersen developed and which, like an HIV test, checks for antibodies. If a vine is found to have the virus it is taken out and those around it are treated with the plant equivalent of anti-retrovirals.
This radical approach appears to be working and now the virus is found in only a fraction of the new vineyards – 0,025% or one vine in 4 000.
Van Rensburg estimates that the leaf roll campaign has cost about R30 million in real terms. This includes the cost of buying in grapes to make up the shortfall after vineyards have been uprooted. But he’s unequivocal that it’s worth it.
“I believe there will be a huge benefit in terms of wine quality and that it will continue to improve year after year. It is the only way to positively change our wine image internationally. South African wines are regarded as cheap and cheerful, when in fact top end South African wine can hold its own with some of the best in the world.”
Besides uprooting infected vines and regularly testing the replanted vineyards, van Rensburg has also launched a blitzkrieg against the mealy bugs which spread the virus. Initially this meant using insecticides to get rapid results, but increasingly Vergelegen’s alien-clearing programme is providing natural solutions.
In what is believed to be the largest private environmental project in the country, 2 000 hectares of Vergelegen land will be cleared of invasive vegetation in a R14 million programme running until 2014. Sixteen million densely packed invasive trees have already been cleared from 1400 hectares.
As the indigenous fynbos returns, it attracts increasing numbers of birds and insects. Amongst the insects that now occur in abundance are ladybirds, the most effective predator of mielie bugs. Birds and other predatory insects also eat other pests that prey on the vines. The fynbos and buchu growing near the vineyards act as natural pesticides, limiting the need to use chemical controls and even fungicides.
Results can already be seen in wines such as Vergelegen’s award-winning V label. Produced on a 2.5 hectare vineyard, whose prime location was selected with the input of French oenologists, it yields 25 barrels/year with collectors happy to pay R800/bottle for the 2004 and 2005 vintages.
Van Rensburg believes the true benefits will, however, be realised in at least 30 years’ time.
“We want to be able to make wine from vineyards that are 30-40 years old as the quality of the fruit gets better over time,” he says.
“There aren’t enough old vineyards in the country. I must ensure that the people who succeed me are able to produce the best possible wine.”
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