Jamie Goode: Copper, sulphur, and the vineyard –tradition vs. sustainability

I love reading about viticulture back in the day. I’m talking here about the time before the mid-19^th century. I remember reading one account of how vineyards were planted in Burgundy (or Bourgogne as we are now supposed to call it) in the past. The winegrower would plant cuttings in the ground in rows around a metre apart. The vines would grow up, and attached to stakes, would begin yielding grapes. It would be pruned back to three buds each year. Then every decade or so, a trench would be dug, some manure added, and the trunk laid down with just a few nodes above ground (three buds), attached to a stake. Then a new trunk would grow up, and this process would be repeated each decade.

After a while, the orderly rows would be lost and the vineyard would effectively be en foule (in a crowd). Any weeding was done by hand, so this didn’t matter. There wouldn’t be trunk disease, because the trunks got no older than 11. Planting could be done by the grower: you just plant cuttings, so no need for nurseries. And genetic diversity would be maintained by massal selection. This was before phylloxera, so no need for rootstocks. And it was before downy and powdery mildew arrived from the USA, so no need for spraying. The manuring when the trunk was laid in the ground would help maintain fertility, as would the lack of deep ploughing, so soil microbial communities would be doing a lot of the work in keeping the vines nutritionally happy.

It was into this relative Eden than the American scourges of phylloxera and the two mildews arrived in the mid-to-late 19^th century that has given viticulture a bit of a sustainability problem.

Now, vineyards are among the most heavily sprayed crops, and it’s no longer possible in most regions of the world to plant from cuttings or do layering (marcottage) or trunk burial. The biggest sustainability issue is from the two mildews, which mean that if you want a crop in most regions worldwide you will have to spray things onto your vines that you’d rather not have to spray.

Spraying vines is expensive. It introduces chemicals into the vineyard that can create problems. And it also causes compaction of soils. Those lucky regions that don’t have growing season rainfall – and we are talking here of Mediterranean-like climates such as vineyards around the Mediterranean, in the Western Cape, and in California – don’t have much of a problem with downy mildew. But powdery mildew is a problem everywhere. While at the beginning stages of the season a bit of dampness does encourage powdery, once it’s there it needs no moisture and likes warm temperatures, making it highly problematic. In New Zealand, for example, growers must spray every week at the peak of the growing season. It’s a major issue there. In a typical season in areas where both downy and powdery are problematic, growers might do 14 spray passes. That’s a lot.

The remedies for powdery and downy were initially discovered quite soon after they arrived in Europe. Powdery came to Europe via the hot house of an English gardener. Edward Tucker, in Margate. In 1845 he noticed it on one of his vines. Tucker looked at it under a microscope, and decided that this disease was very similar to peach mildew. And back in 1821 an Irish gardener called John Robertson had successfully used sulfur to control peach mildew, so Tucker tried it too, and it worked. Robertson had mixed sulfur with soap, whereas Tucker mixed it with lime. Despite this successful treatment, powdery mildew spread, across the UK and to France. Before long, it was a major problem across the vineyards of Europe. It was first spotted in French vineyards in 1847, and then in Italy in 1849. In the early 1850s it caused massive problems economically, as winegrowers learned to get to grips with the best ways of applying sulfur as a remedy. Since then, it has been an ever present in the vineyards of the world.

Downy mildew arrived in France in 1878, most likely via the American vines imported after phylloxera broke out. The chemical fix, still used today, was discovered by Pierre-Marie-Alexis Millardet who made this observation fortuitously. In October 1882, Millardet was in the vineyard of Château Beaucaillou in the St Julien region of Bordeaux, and noticed something strange. Rather than leaves ravaged by downy mildew, he saw vines with a healthy canopy. The leaves had been covered with Verdigris – copper sulfate mixed with lime – to deter thieves. It gave them a bluish green colour, but it also stopped the mildew in its tracks. Over the next two years, Millardet revised this treatment, which became known as Bordeaux mixture. The recipe is simple. Take 100 litres of water and 8 kg of copper sulfate, and mix them. Then make a milk of lime, by dissolving 15 kg of rock lime with 30 litres of water. Just before spraying, combine the two, and use it all up within a day or two. 50 litres of this concoction treated 1,000 plants. So, to treat one hectare would take around 500 litres. This solution was effective, and variations on the theme of this Bordeaux mixture are still in use today.

If you farm organically, these chemical remedies are permitted. If you aren’t organic, you can use potassium phosphonate alongside copper for downy mildew and this is very effective, reducing the amount of copper needed. Or you can use what are known as systemic fungicides, which work from the inside of the vine and specifically target certain mechanisms of action of the disease-causing organisms. These are generally more effective that copper and sulphur, although conventional growers may well use a mix of the older remedies and the newer to stop resistance occurring to the systemics. Copper and sulphur are what’s known as contact fungicides, and they work only if they are covering the vine’s surface. If it rains, they get washed off.

Neither approach is all that sustainable. The systemics may affect the fungal populations in the soil, but this hasn’t been well studied. Sulphur isn’t too bad, but residues often remain on the grapes that can then cause fermentation issues, and it needs applying frequently, leading to soil compaction and increased carbon footprint. Copper is the real baddie, because it ends up in the soil and is toxic to soil life. But if you are organic, there are no real alternatives. Various teas and preparations can give a little protection, but alone can’t give the protection that copper can.

The truly sustainable solutions? Grow vinifera only where disease pressure is low. Elsewhere, we really need new vine material if we want to farm sustainably. A lot of breeding work has been taking place to produce hybrids that have the true resistance genes against powdery and downy, and more than one copy of each to stop the disease becoming resistant to them in turn. And these are backcrossed with vinifera varieties to produce a resistant vine that’s mostly vinifera and has good wine quality. These are catching on in Europe, and they have just started being imported to Australia and New Zealand. Australia also has its own disease-resistant vine breeding program.

There’s also interest in taking well known vinifera varieties and fiddling with their genetics to make them resistant. Genetic modification, introducing the resistance genes from American and Chinese varieties, is possible and has been done, but people aren’t ready to accept genetically modified vines right now. An alternative approach is gene editing, introducing nothing but using special genetic scissors to take out susceptibility genes, and thus making vinifera more-or-less resistant. Trials have gone as far as experimental plantings of edited Chardonnay in Italy, but protestors sabotaged them. These aren’t considered genetically modified in many countries, but Europe is sitting on the fence a bit.

True sustainability is something we should be aiming for. In many climates, while I love organics, it’s really not all that sustainable because of all the spraying.

• Jamie Goode is a London-based wine writer, lecturer, wine judge and book author. With a PhD in plant biology, he worked as a science editor, before starting wineanorak.com, one of the world’s most popular wine websites.