2008 January | homewineschool.com

Noble Rot

On January 30, 2008, in Making Sweet Wine, Noble Rot, Viticulture, wine geeks, by ngorevic

Noble Rot is a form of the botrytis cinerea fungus that can form some of the greatest sweet dessert wines in the world. For this to happen, the exact right conditions must develop, and there are only a few places in the world where this happens, most notably in Bourdeaux (Sauternes) and Germany. It requires damp mornings and dry afternoons. When this happens, the rot attacks the ripe grapes, and eats the water inside the grapes without breaking the skin. By sucking out the water, the sugar in the grape becomes concentrated, allowing a wine to be produced that is both high in alcohol and sugar. In addition, the fungus flavors the wine in it's own special way, adding notes of honey and marmalade. This process is tricky, and requires a great deal of hand-picking. Pickers must go through the vineyard several times, each time picking only those grapes that are affected by the rot in just the right way. Some years the fungus just isn't created, and entire crops are lost. Because of the unpredictability, and extreme level of care required to produce these wines, they are always very expensive. And they are amazing!

Diseases

On January 30, 2008, in Diseases, Viticulture, wine geeks, by ngorevic

Most diseases these days can be combated by spraying the vines protectively throughout the growing season. This is usually done by tractor, although in extreme cases helicopters or planes can be used. Diseases take the form of mildew, rot, or other long term diseases.

Mildew comes in two main forms, Powdery, and Downy. Powdery Mildew, also called Oidium, attacks all the green portions of the vines, forming powdery spores. If it reaches the buds or the grapes, the grapes do not ripen properly and eventually split open. Spraying the vines with sulphur solves this problem. Downy Mildew, called Peronspera, is similar to phylloxera, in that it came over from America to infect European vineyards. It also attacks the green portions of the vine. Downy Mildew thrives in damp conditions, and can be stopped by modern fungicide sprays.

Rot can take three forms, grey, noble, and black. All three are the same fungus, botrytis cinerea, and are created in damp, humid conditions. Grey rot affects the young berries, reducing yield quantities a great deal. Spraying can halt the process, but it must be eradicated before the grapes begin to ripen. Noble rot is actually a beneficial form of the fungus, that can create outstanding dessert wines. More on this in a separate post. And black rot is brought about by heavy rains, affecting the leaves and vines. Black rot can be prevented by spraying something called Bordeaux mixture, a solution of lime and sulphate.

Vines are also susceptible to long term diseases, and include fungal as well as bacterial diseases. Eutypa and Phomopsis are two fungal diseases that can combine to form a condition known as "Dead-Arm," which can reduce yield substantially, without affecting quality. Pierce's, a bacterial disease spread by insects called sharpshooters, can also reduce yields. All of these fungal and bacterial diseases are currently without cure, and prevention by cordoning off vineyards can often be the only way to prevent them. With these diseases, as well as other long term viral diseases that attack vines, once they have become widespread, the vineyard will have no choice but to dig up all the vines, sanitize the land, and plant entirely new cuttings.

Phylloxera

On January 30, 2008, in Phylloxera, Vineyard Pests, Viticulture, wine geeks, by ngorevic

Phylloxera is a bug that feeds on a vine's roots. It is an aphid native to North America, and its effect on wine production is legendary. In the 1860's phylloxera managed to make its way over to Europe and proceeded to devastate European vineyards. In much the same way that Europeans brought viruses that Native American's immune systems were unprepared for, the European vines had no natural resistance to Phylloxera. As a result, almost all European vineyards were completely destroyed, and an international effort to restore wine production started. French wine production in particular at one point was thought to be completely lost.

Fortunately, someone discovered that the good old American table grape vines, vitis labrusca, were unaffected by phylloxera. American rootstock was then sent to Europe, and the vitis vinifera vines were grafted onto the labrusca rootstock. To this day almost every single vine planted in the world is grafted in this way. There are only a few places, mostly in South America, that have escaped the effect of these deadly bugs.

When I heard the story of phylloxera, my first thought was, does the labrusca rootstock affect the taste of the grapes and therefore the wine? Apparently it doesn't. While the labrusca grapes make terrible wine, apparently the roots are virtually identical. There are actually a few benefits to this little bug. Before anyone understood phylloxera, wine production (good wine, anyway) in the United States was non-existent. Thomas Jefferson had famously brought back many vine clippings from France to try and plant at Monticello, and was totally unable to produce any grapes. No one understood why that was until they discovered that it must have been the phylloxera that was eating Jefferson's vines. So as a result of this bug, and the international cooperation it necessitated, we have wine in the United States. Hooray for us!

Vineyard Pests

On January 30, 2008, in Vineyard Pests, Viticulture, wine geeks, by ngorevic

There are several different pests that can affect grape growing, and increase the cost of production. The most important of these is Phylloxera, which I'll discuss in a separate post. In addition there are the following threats:

Grape Moths: These are caterpilars that attack the buds in springtime and the grapes when they grow. These pests can be avoided by spraying insecticides.
Red and yellow spider mites: These appear mostly in vineyards with hot dry weather. They flourish because insecticides have killed off their natural predators. Mites eat the leaves of the vine, taking away from growth. There are special sprays used to get rid of them, or in organic vineyards, natural predators are used.
Nematodes: These are microscopic worms that attack rootstock. Once they infest a vine, they're almost impossible to get rid of, so the best way to deal with them is to take preventative measures, including using resistant rootstock and sanitizing the soil before planting.
Birds and animals: Many techniques are used to scare away birds, like installing speakers that play loud noises. The most effective method is to lay protective nets over the vines, but that is very expensive. Larger animals like deer will also try to eat grapes, which may require protective fencing.

Yield Management

On January 30, 2008, in Viticulture, Yield Management, wine geeks, by ngorevic

As I've noted earlier, the amount of grapes a vine produces can have a direct effect on the quality of the grapes produced. If vines are allowed to produce too many grapes, the amount of sugar will be spread among those grapes and diluted too much to make good wine. In Europe, yield rates are legislated for each grape variety in each area. While there are no such laws in the New World, when good wine is the desired product, yield rates must be considered. Yields are usually expressed in weight or in volume. When expressed in weight, the yield will be in tons of grapes per hectare, and when it is in volume it will be hectoliters per hectare.

Here is a list of the different factors that can affect yields:

The number of vines per hectare.
The number of buds per vine, determined by pruning.
The number of shoots, which depends on the soil and climate conditions, and the number of buds per vine.
The number of clusters per shoot, which described the fruitiness of a vine, and is determined in the spring when the bud forms.
The number of berries per cluster, which is determined by the flowering process, dependant on the weather during flowering. This is the most unpredictable phase.
The weight of the berries. This is determined by the grape variety and how much water reaches the vines, either through irrigation or rain. The nutrient supply is also a factor.
Green harvesting. This is a process in which people will go through the vines and hand-pick out excess bunches of grapes in an effort to reduce yield.

As you can see, there are many factors that influence the amount of yield that will come from a vineyard. Each one of these factors involves a decision on the part of the winemaker, and each of those decisions will increase or decrease the cost of production. Hopefully every decision that increases the cost will result in a better bottle of wine.

Training

On January 30, 2008, in Training, Viticulture, wine geeks, by ngorevic

After Pruning, the canes still remaining will be trained. There are 4 basic types of training systems, and one will be chosen based on the climate of the vineyard, and the yield required. The purpose of training is to control the way the grapes and leaf cover are exposed to the sun. In a vineyard with cold temperatures or a lot of wind, the grapes might be trained low to the ground to help them absorb reflected heat from the ground. The training system may involve wires, also called pergolas, that the grapes are tied to, or they may be free standing. The four types of training systems are:

Bush training or gobelet: This system is used in warmer regions like Beaujolais or the Rhône valley. The vines are left free standing, without the use of any pergolas, and about 4 or 5 spurs are left. This system leaves the grapes bunched closer together, so is not used when the potential for rot is present. It also leaves the grapes closer to the ground, so it is not used when the risk or frost is high.
Replacement cane: This system is called guyot when it is used in Burgundy and Bourdeaux. The canes are trained along horizontal wires, and new canes are used every year. In a single guyot system, one cane is used, and in a double guyot, two.
Cordon spur: In this system, the trunk of the vine is grown laterally, with several spurs left on its length. This can be a low cordon system, like the Cordon de Royat system used in Champagne, or a high cordon system, such as the Geneva Double Curtain.
Parral or Pergola: In this system the vines are trained high on the wires, with the grape bunches hanging around head height. The primary purpose of this system is to give leaf cover in hot climates.

Pruning

On January 29, 2008, in Pruning, Viticulture, wine geeks, by ngorevic

The primary purposes of pruning is to select which buds will form shoots for the upcoming harvest and to prepare the vine for the fruiting process in harvests in the future. Pruning can also help control the number of buds, which has a direct effect on the yield of a vine, another factor that can affect the quality of the wine. In Europe, the pruning method is often controlled by law.

There are two types of pruning-- spur and cane. In spur pruning, several short spurs are left on the vine. In cane pruning, one or two canes are left, each with 8-15 buds.

Planting

On January 29, 2008, in Planting, Viticulture, wine geeks, by ngorevic

Vine planting is a complicated process. This makes it difficult for winemakers to keep up with trends, because it can take up to 5 years from first planting before they can successfully harvesty grapes to make wine. Vines are planted to either replace old vines, or start new vineyards. Almost all vines consist of a European vine grafted on to an American vine rootstock, because of its resistance to phylloxera.

When a vine is planted, it can produce grapes for about 35 to 50 years. As it grows older, it will produce less and less grapes, but often those grapes will be of higher quality, leaving the winemaker with a decision of a quality versus quantity. When vines are grubbed up, the land usually needs to lie fallow for at least 3 years before planting new vines, so a vineyard has a cycle of land usage that must be monitored. The first yield usually will not come until the 3rd year of harvesting, and often that first harvest will not be used to make wine.

After the new vines are planted, the European rootstock is all that will be visible above the soil. This visible base is called the scion. During the spring, shoots bearing tendrils and leaves will grow from the scion. Over the next winter, those shoots will mature and turn brown, when they are called canes. When grapes eventually grow, the grow from shoots formed that spring from these canes. Sometimes a cane is pruned short, leaving only a two or three buds, and then it is called a spur. By the end of the next year, the canes and spurs are usually removed and new canes and spurs are allowed to grow.

In addition to planting, the way the vines are trained and pruned will have a large effect on how the wine turns out. I'll move onto to those topics next.

Aspect and Slope

On January 29, 2008, in Aspect and Slope, Soils and Topography, wine geeks, by ngorevic

The aspect and slope of a where a vine is planted can also have a large effect on the grapes. A 30° slope facing towards the equator can double the amount of sun the grapes receive. In a flat planting, the vines on either side of any given row will block sunlight to the rows next to it. But when the vines are on a hill, the sun can hit all the grapes hanging down on every row. A sloped hill also offers better drainage, and more air circulation.

The hill also complicates the viticultural proces, because it is harder and therefore more expensive to work on a hill. It often makes mechanical harvesting impossible. In Burgundy, for example, a Grand Cru wine can be grown right next to a Cru Bourgeois, but the Grand Cru will all come from a hill, while the Cru Bourgeois will be on the flat plain right next to the hill.

Viticulture

On January 29, 2008, in Viticulture, wine geeks, by ngorevic

Viticulture is everything that happens in the vineyard before the grapes are turned into wine. It includes selection of vines and rootstock, decisions on whether or not to irrigate, planting techniques, harvesting times, and many other aspects that all have a huge impact of the how the wine will turn out. Viticulture is distinguished from Vinification, which is the process of turning the grapes into wine.