Viticulture or grape growing, as distinguished from Viniculture which is winemaking.


Information on the annual growth cycle of the vine and canopy management can be found by selecting the following link “Introduction & Pruning”.


The grapevine thrives between 30 - 50 degrees north latitude and between 30 - 40 degrees south latitude. Wine making starts around 30 degrees, here the climate tends to be hot, but as you move closer to 50 degrees latitude the climate is much cooler. If we divide the world into two groups, cool climate and warm climate, we get a general feel for the style of wine able to be produced. Cool climate wines often exhibit lower alcohol, higher levels of acidity with fresh clean and defined aromas. Hot climate wines tend to produce wines that are higher in alcohol, lower in acidity.



The vine has very low nutritional requirements. It requires only three major nutrients:

  1. Bullet    Nitrogen (N)

  2. Bullet    Phosphorus (P)

  3. Bullet    and Potassium (K)


and six minor nutrients:

  1. Bullet    Magnesium (Mg)

  2. Bullet    Manganese (Mn)

  3. Bullet    Iron (Fe)

  4. Bullet    Zinc (Z)

  5. Bullet    Copper (Cu)

  6. Bullet    and Boron (B)


Grapevines are part of the genus Vitis. There are many indigenous species of grapes worldwide but the overwhelming majority of wine produced is from the species Vitis vinifera. Vinifera is native to Asia and Europe and has been spread by humankind throughout the Old and New Worlds.


Within the species Vitis Vinifera there are over 5,000 named cultivars/varieties; only a fraction are grown commercially, for more information see “Grape Varieties”. Some terms that relate to vine types include:

  1. Bullet    Varietal/Variety - a subspecies of grape, especially of Vinifera e.g. Chardonnay etc.

  2. Bullet    Clone - vines descended from a single plant by cuttings (asexual reproduction)

  3. Bullet    Mutation - a vine that has developed different characteristics through imperfect reproduction of cells as it grows. This is a natural but slow evolutionary process that ultimately leads to the development of new subspecies.

  4. Bullet    Cross or Crossing - the offspring of sexual reproduction of different subspecies within the same species (e.g. Cabernet Frank + Sauvignon Blanc = Cabernet Sauvignon).

  5. Bullet    Hybrid - the offspring of sexual reproduction between two different species (e.g. a hybrid of Vitis Vinifera and Vitis Labrusca)


The most fundamental aspect of any vineyard is the ground in which it is planted and the quality of the soil affect the character of the wine. There are a number of parameters that go into a soil’s makeup:

  1. Bullet    the parent material or rock of which it is comprised, they affect the ambient temperature of the mesoclimate by radiating heat

The size of the particles the soil is made of:

  1. Bullet    clay is made of very fine particles, has the greatest capacity for holding nutrients and water

  2. Bullet    silt has larger particles than clay

  3. Bullet    sand has larger particles than silt and has the least capacity for holding nutrients and water

  4. Bullet    the chemical composition of the soil (minerals) that create good soil structure by maintaining the soil’s friability and porosity

  5. Bullet    the organic matter and nutrients in the soil, makes clay soils more friable (easily crumbled); helps sandy soils retain nutrients and water



Major wine diseases and pests:


Viral Diseases:

Leaf roll - change in color and downward rolling of the leaf blade responsible for delayed crop ripening and reduced yields (the pigments that were to develop in the grape end up staying in the leaf). Leave roll is also responsible for the lovely gold and red vine leaves in autumn. The only known remedy for leaf roll is vine removal. The disease is spread by propagating infected vines.



Fan Leaf - is responsible for unusual growth patterns in the vine: short internodes, abnormal branching, malformed leaves that look like fans, small clusters, poor fruit set and shot (or seedless) berries.





Fungal Diseases:

Esca - is one of the earliest known fungal disease. California knows it as black measles. It’s a problem in warm climates, where it can kill vines suddenly in hot weather. The problem has grown since 2001, when sodium arsenite, the only product that keeps the sickness in check, was banned as a carcinogen. With no alternative treatment, the disease is on the increase, notably throughout southwest France, particularly Cognac and Armagnac, but also in Bordeaux.


Eutypa dieback (dead arm) - sometimes grape cancer is a disease of grapes caused by a deep-seated wood rot of the arms or trunk of the grapevine. As the disease progresses over several years, one or more arms may die, hence the name "dead arm". Eventually the whole vine will die. Eutypa dieback is caused by Eutypa Lata which infects fresh pruning wounds when there is adequate moisture on the vine, such a just after a rain.


Powdery Mildew - also known as oidium, is a fungal disease native to North America. Although it doesn’t affect native American varieties, it can devastate a Vitis Vinifera vine in many insidious ways. Powdery Mildew attacks the entire vine with white cobweb-like filaments. If an infection takes place before flowering, yields are reduced. If the clusters are infected, they will not reach full size or achieve maximum pigment development and the fruit will have undesirable flavors. The fungus can survive over
winter on the vine and is therefore tough to eradicate. Its germination is not dictated by humidity and it thrives in warm, dry conditions within a shaded canopy. Sunlight inhibits germination of the spores. A sulfur spray is most effective in eliminating this threat.


Downy Mildew - also known as peronospera, is a fungal disease native to North America. Although native American varieties are resistant, Vitis Vinifera is highly susceptible. Downy Mildew attacks the green portion of the plant and thrives in warm humid weather. In its beginning stage, a vine leaf looks as if it has oil spots, as spores germinate on its underside and spread outward with white cottony filaments. A severe infection will cause the vine to loose its leaves. which delays ripening. Copper sprays such as “Bordeaux mixture” (copper sulfate) are effective in curtailing the spread and outbreak of Downy Mildew.


Botrytis - (botrytis cinerea) also known as noble rot, the fungus removes water from the grapes,
leaving behind a higher percent of solids, such as sugars, fruit acids and minerals. This results in a more intense, concentrated final product. The wine is often said to have an aroma of honeysuckle and a bitter finish on the palate and produces some of the finest sweet wines in the world. The fungus germinates and spreads when humidity is at least 90 percent and the weather is warm (59 - 68 F), if however the weather remains moist, noble rot quickly turns into gray or bunch rot and ruins he crop. Botrytis will alter the white grape’s (Sauternes - Sémillon (mainly), Sauvignon Blanc, and Muscadelle) composition positively but will negatively affect red skinned grapes by damaging pigments and producing rotten off-odors in the finished wine.


Black rot - is a fungal disease native to northeastern North America that attacks the vine in mild,
wet weather. It originates as a black spot on the shoot, leaves and berries and spreads along the vine tissue. It’s responsible for crop loss but can be controlled through the use of fungicides.




Bacteriological Diseases:

Pierce’s Disease - is a bacteriological contamination of the host vine resulting in premature leave fall. First, large dead areas appear on the leave and expand until the entire leave falls from the vine.
The disease is spread by the glassy-winged sharpshooter and leafhoppers, insects that feed on an infected vine and than transmit the bacterium to a healthy vine. Disease pressure is highest in the southern United States but has expanded to other areas where topography favors an environment suitable for the sharpshooters and leafhoppers, such as near streams or wetlands with marsh grasses.



Crown gall - is a bacterial disease that causes large tumors or growths to appear on the trunk of
the vine. These tumors girdle the vine, strangling the portions above it so the vine withers and dies.





Insects:

Phylloxera - no insect has been credited with more vineyard devastation than the tiny root-eating louse phylloxera. Phylloxera, originally native to eastern United States. These tiny, pale yellow sap-sucking insects feed on the roots of grapevines. In the late 19th century the phylloxera epidemic destroyed most of the vineyards for wine grapes in Europe, most notably in France. Phylloxera was inadvertently introduced to Europe in the 1860s, possibly on
imported North American vines. Because Phylloxera is native to North America, the native grape species there are at least partially resistant. By contrast, the European wine grape Vitis vinifera is very susceptible to the aphid. The epidemic devastated most of the European wine growing industry. In 1863, the first vines began to deteriorate in the southern Rhône region of France. The problem spread rapidly across the continent. A huge amount of research was devoted to finding a solution to the Phylloxera problem, and two major solutions gradually emerged: hybridization and resistant grafting European grape varieties onto disease-resistant American rootstocks.



Viticultural Practices


Organic Viticulture -   An approach to farming that seeks to maintain and improve the productivity of  the land by encouraging and enhancing natural biological processes. The foundation for healthy plants and animals is a healthy soil.  Great attention is paid to nurturing the soil by the use of composts, cover crops, rock minerals and natural fertilizers.  Plant disease and pests are

controlled through the use of crop rotations, resistant varieties, cultivation, biological pest

controls and botanical controls.  The use of synthetic chemical  fertilizers and pesticides are prohibited in certified organic production. It does however allows applications of natural inorganic elements such as sulfur and copper.


Integrated Pest Management (IPM) - is often incorporated into organic viticulture. The IPM strategy is to get the “good bugs” to eat the “bad bugs” in the vineyard. This is achieved by releasing beneficial insects into the vineyard or by enticing them into the vineyard through the calculated planting of certain cover crops.


Biodynamic Viticulture - Biodynamics is the name given to the ideas and ideals, principles and practices offered by Rudolf Steiner (1929) for agriculture and it takes organic practices one step further. Although biodynamics can be understood in many ways, it is foremost an attempt to understand how nature works, how the substances and forces at work in nature interact and form a whole, living physiology - and how to work successfully, naturally and ethically within nature's system of substances, forces and beings.


Sustainable Viticulture - In environments where the practices of organic viticulture are difficult or impossible to implement due to disease pressure or insect populations, growers have adopted a method of sustainable viticulture.


 

Viticulture

Saturday, January 19, 2008

 
 

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