Viticulture 4 Virgins

Part III - Vineyard Dramas

This is not the place where we discuss the current trend of theatre or Jazz amongst the vines. This is much more dramatic!

There's a multitude of pests and diseases that can be inflicted on a vineyard, much the same as any other fruit plantation. By far, the most destructive would have to be the soil-borne pests - Phylloxera and Nematodes.

Phylloxera

Phylloxera has such a torrid history in the wine industry that it could easily make up a page on this site of its own.

This aphid-like insect creates drama of Shakespearean proportions. Talk about rocking the vineyard - this creature will turn your vineyard to rocks. Literally.

A happy-go-lucky, adaptable nature sees this minute [adults are about 1mm long] critter travel easily all over the world, wherever vines are sent.

Originating in America, east of the Rocky Mountains, Phylloxera first hit France in 1863, no doubt on imported vines. In a short time, the pest brought the French wine industry to its knees - single-handedly destroying over 1 million hectares of vines, and almost finishing off the wine industry altogether!

During summer, Phylloxera lives on the leaves of the grape vines, wallowing in the warmth, laying eggs and playing cricket for 4-7 generation-cycles. Towards the end of summer, it flies south to the soil to embed itself into the grapevine roots, forming galls. The decay of these galls eventually kills the vines.

Unfortunately, dead vines are the sympton of infestation.

The solution for this pest in phylloxera-prone areas lay in the indigenous American vines. Having lived with the pest for centuries, native vines had become tolerant. Not resistant, mind you, as the phylloxera still hangs around. They managed to survive despite phylloxera staging performances on leaves and roots. The answer for Europe: graft the desired grape vines onto indigenous American phylloxera-tolerant rootstocks.

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Nematodes

These eelworms attack the roots of the grape vines, forming galls similar to phylloxera. The main sympton that a vineyard is infested with nematodes is stunted vines.

Unfortunately this is often misdiagnosed, and once infestation sets in, there's only one solution - replant the whole lot on nematode-resistant rootstocks.

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Practice Safe Vineyard Visiting

This is serious stuff. Mention these two pests to an uninfected vineyard owner, and you see his eyes widen in terror.

As these particular pests are soil-borne , they can easily stick to your shoes, or car tyres if you visit an infected region. All you have to do is walk into virginal vines in those shoes, or drive through the vineyards with those tyres, and you've sentenced them to death.

That's why it's important to be aware when you are travelling from vineyard to vineyard to do your cellar door shopping. As much as you'd love to frollick among the vines, always ask first , heed NO ENTRY signs, and be understanding when you are refused.

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And There's More ...

Soil-borne pests aside, there's a myriad of other critters to wreak havoc and create drama in the vineyard:

• Moths and their larvae
• Scale
• Mealybugs
• Cicadas
• Borers
• Mites
• Snails
• Grasshoppers and locusts
• Beetles
• Birds

Not to mention the diseases - mildews, bacterias and viruses. All contribute to the degradation of quality in both the fruit and the resulting wines.

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Fightback!

Different vines show different levels of susceptibility to disease. For example, Cabernet Sauvignon and Semillon show greater resistance to Downy Mildew, making them favourites in warmer, more humid climes.

Nevertheless, until scientists successfully clone disease-resistant vines [that's on the cards ...] or create nano-bugs which traverse the vines combatting these pests and diseases [plausible?] , control comes in the form of a routine fungicide and pesticide program in the vineyard.

Sulphur formulations are common, but there are other pesticides used. Mind you, this is about CONTROL only. If scheduled spraying doesn't occur, and control of the pests is lost, the vineyards need to be drenched in chemicals to get back on track.

Control poses another challenge for warm and hot vineyard regions with high levels of humidity. Sulphur formulations can damage vines if used in temperatures above 32ºC, and can taint wines if used within a month of vintage.

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Biotechnology and Genetic Engineering

The light-hearted inference above to scientists cloning and creating nano-solutions to these problems is not as futuristic as it sounds.

Biotechnology in recent times has harnessed DNA technology which enables new, disease-resistant plant cultivars by way of genetic engineering. This has been a huge boost for agriculture and the earth's ability to feed its population, and the wine industry is no stranger to the technology.

Genetic engineering enables the manipulation of DNA to isolate genes responsible for a particular action, response or characteristic. These isolated genes can then be introduced to other plants to give them the same benefits.

For example, the resistance to Phylloxera that America's hybrid vines have taken centuries to form can be introduced to non-resistant vines without affecting the desirable qualities of a those grapes. This means that more vines can be grown on their own rootstocks rather than being grafted onto resistant American hybrids. The resulting wines will be truer to form, and of better quality.

Genetic engineering also opens the door to introduction of genes from other sources - eg bacteria, animals ... whatever. Imagine being able to introduce a gene from bacteria that gives insecticide qualities to vines? No more need for sprays! Which means safer, better quality wines.

The downside is consumer attitude to genetic engineering. Whilst it has been introduced quietly into many of our foods and beverages, it is not widely accepted. People have ethical concerns about scientists 'playing God', and environmental impact or health issues. There are socio-economic concerns about who 'owns' the technology and the widening gap between 'haves' and 'have-nots'.

Like most resistance to change, many of these concerns are driven by fear of the unknown. The best approach the wine industry could take is public education and honest labelling of wines.

The status quo is chemical weaponry against attacks by disease and pests in the vineyard. It comes down to a question of what we are and are not willing to accept in the name of good wine!

Last updated: Monday, June 18, 2007