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For ten years now, hail nets have been protecting many vineyards in the Austrian wine-growing region of southern Styria. Vintners and the director of the viticulture school Silberberg report on the experiences, advantages and disadvantages.

In July 2009, a hailstorm hit Erwin Tschermonegg 's vineyard in Glanz on the South Styrian Wine Route and destroyed the entire harvest in a matter of minutes. This was the trigger for the intensive study of the topic of protecting oneself with hail nets. Tschermonegg, his fellow vintner Willi Sattler from the STK (Steirische Terroir & Klassikweingüter) winery Sattlerhof in Gamlitz and the Styrian Education Centre for Fruit and Viticulture in Silberberg near Leibnitz began to systematically research the advantages and disadvantages of hail nets in the vineyards. Ing. Reinhold Holler, director of the technical school Silberberg, reports on the experiences of his trials: "At that time we covered every second row of an acre with nets. The data of the test series did not show any differences in the must and wine analysis, although the nets reduce the amount of light by ten percent. The aroma profile was rated significantly more aromatic in one tasting of the test wines for Sauvignon Blanc, but not in another. There was also no change in the aroma profile for Weissburgunder. So the net alone does not change the wine."

Foliage work is crucial

Willi Sattler adds: "The temperature curve under the net is already different than without it, in spring it is clearly warmer underneath. That means earlier budding. But we want to delay budbreak, so we pull the nets down later. Otherwise this would happen when the shoots are tied up. That is one more operation, but if I can avoid disadvantages so easily, I accept the higher costs. After all, you also save yourself some work because you don't have to attach the shoots any more."

An important criterion is the foliage work, especially with the Styrian leading variety Sauvignon Blanc. It is particularly important to keep the grape zone and the foliage wall loose and airy, which means more effort. Willi Sattler and Erwin Tschermonegg have had similar experiences: "The extra time I invest in building up an airy foliage wall I save later because the shoots grow straight up. I also get fewer stingy shoots."

How far do we want to go with technologisation?

The almost uniform structure of the foliage walls is one aspect that keeps STK winemaker Johannes Gross from Ratsch away from the hail net: "The grapevine is a climbing plant that originally climbed up trees. It still wants to do that today, it strives towards the light. Under the net, I force it into the shade, under the crown of the tree, so to speak, and do not allow it to grow into the crown. I restrict it. We asked ourselves in the family: How far do we want to go with this technologisation? Do we orient ourselves according to the vine - or should the vine only orient itself according to us? Wouldn't a glass house over the vineyard be even better than the net on the side? We have decided that we want to focus on the horticultural aspects and work every single plant by hand."

At the same time, Johannes Gross is not dogmatically opposed to hail nets, even though he does not like them aesthetically: "They change the reflection of light. We have also had experiences with nets and find that the grapes ripen differently. Not qualitatively worse, but that is a question of principle. However, we in Ratsch are not as affected by hail as other areas. And I cannot rule out the possibility that we will have to resort to nets in the future. At the moment, anyway, we want to do without it."

Suitable for organic viticulture

Reinhold HollerReinhold Holler

In the humid climate of southern Styria, dew formation is an issue because 1,000 mm of rainfall, or 1,000 litres per square metre per year, is normal there. In Silberberg Reinhold Holler has found that "dew formation happens at the net and not at the leaf. In addition, precipitation rolls off more easily, it doesn't get as damp under the net. There are no differences in rot and fungal infestation. In addition, we could not measure any effects on infestation by cicadas and cherry vinegar flies. Wasps don't come out of the net as well, but they feel more comfortable underneath anyway."The net also offers better protection against larger animals such as birds, deer and wild boar - but only if it is carefully stapled together at the bottom.

No vintner has been able to observe any effects on the effectiveness of plant protection. Willi Sattler even reports advantages: "That was my biggest fear. In organic viticulture, we have to wet the whole leaf because our products only work at the contact points. If you don't spray but spray, i.e. mist the products heavily, the net even has a better effect because it distributes the mist more finely."

The extra work involved in manipulating the nets is made up for by the time saved in knitting them in, where the shoots are brought into the wire frame. Especially as this is a job that has to be done quickly. Harvesting is also quicker, as there is less need for selection. Grapes that are lying against the net and damaged by hail are simply cut to the ground, because these are volume losses in the per mille range.

Most winegrowers accept the fact that the black nets above the rows of vines do not look so nice, especially before the leaves form. Erwin Tschermonegg says: "When we planted the first five hectares in 2011, neighbours and visitors complained: Why is he disfiguring our beautiful landscape? After the next storms, the hostility quickly died down because they saw that it helps. I can live with this criticism, because I have already experienced twice that our farm was almost destroyed by storms: in 1980 at my father's place, when there was also frost. After the catastrophe in 2009, we had a 70 percent loss in 2010 - a year without hail - and even in 2011 we did not have the full yield again. In the past, every black cloud frightened me, but today I stay calm because I know that not much can happen. This has increased my quality of life. We are aiming for full netting of our vineyards."By the way, the cost of netting per hectare is between 7,000 and 9,000 euros on steep slopes.

The best insurance: reserves in the cellar

Hail nets, however, mean a lot of plastic in the vineyards, with accompanying symptoms such as abrasion and fine dust. No one disputes that, but Reinhold Holler points out: "If waste is blown from the roadsides into the vineyards, that's much worse. After all, the hail nets are maintained, we expect them to last 30 years." Erwin Tschermonegg confirms this: "Our ten-year-old nets show no signs of wear, are elastic and not faded by the sun. In orchards there are nets that have been in use for 50 years."

Willi Sattler emphasises: "Viticulture is a cultural technique, it is an artificially created landscape anyway. So I accept that nets do not beautify the landscape. Because they are an insurance, an aid to quality assurance. If you can help yourself, you should do it - because hail insurance hardly replaces anything. And I have a responsibility towards my farm, my family, my employees and customers." He agrees with his STK colleague Johannes Gross: "The best insurance is always to have at least one whole harvest in the cellar to fall back on. "

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Photos: © Wineries; College of Agriculture and Forestry Silberberg

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