DELEAFING OR VINEYARD LEAF REMOVAL EQUIPMENT
Foliage or leafage, in vine leaves is considered as a whole. It is fundamental part of the canopy and is composed of the main organs of photosynthesis and transpiration in the grapevine. It also provides shade to bunches and may be subjected to pruning. Deleafing is the process of removing leaves from the cluster area around the vine, usually directly above and directly below the fruit. This is commonly referred to as removing the basal leaves on the canopy where the buds are positioned or simply as cluster area leaf removal.
Leaf removal in the vineyard is the operation performed after verasion consisting of cutting off some of the vine´s leaves, which aims at improving sun and wind exposure of the bunches as well as limiting its vigor. It is very common practice in temperate and cool areas and helps to avoid diseases caused by fungi as well as to the ripening of the fruit. Conversely, in very warm and dry areas, it is not usually practiced for foliage protects bunches from withering due to excessive heat.
Leaf removal is a practice aimed at helping to control botrytis bunch rot and other bunch rots, and at improving grape composition and therefore wine quality. Typically the leaves are removed around the bunches to increase exposure to the sun and wind. The bunches dry out more quickly after dew and rain so that moulds are less likely to develop. Increase exposure to sunlight helps the berries produce more of the phenolics important in wine quality. Grape sugars are also increased and malic acid reduced, both of which contribute to improved wine quality.
For optimal effects on wine quality, leaves should be removed several weeks before verasion, although it is more usual to remove them at its onset. In Europe it is common to remove leaves nearer to the time of harvest, primarily to reduce the risk of botrytis bunch rot. Leaf removal is also used to improve the color of black and red table grapes. Traditionally leaf removal has been done by hand, requiring about 50 hours of labor per hectare (2,5 acres), but machines which take less than five hours per hectare to remove leaves by suction and cutting have been developed.
Recent studies around the world have questioned excessive leaf removal in warm to hot climates, because there can be negative effects on fruit composition and wine quality. This is due to the bunches being heated by the sun, leading to undesirably high temperatures within the grape berries in the afternoon when the temperature is also higher. The alternative is to do less removal on the western side of the canopy.
Decreasing dependence on agrochemicals in the vineyard has led to renewed interest in leaf removal in both Old and New Worlds. As well as making the fruit less prone to fungal diseases by improving aeration, leaf removal can also increase the effectiveness of such chemicals as may be applied to protect the fruit.
PRE-DELEAFING AT BODEGAS URBINA LA RIOJA
The pre-delafing or early vineyard leaf removal of the vine is a technique whose main purpose is to regulate grape production. This process is carried out around flowering, as opposed to the classic, later leaf removal. In this way, it significantly helps to modify the bunch weight, the number of berries and the yield per plant.
It is carried out during the flowering or fruit setting period (transformation of the ovary into fruit). This green pruning operation is effective to reduce the yield per plant by 15 to 50%, smaller, loose bunches are obtained and also the incidence of mildew, powdery mildew and Botrytis rot is significantly reduced, being able to create a better quality of the grapes and wine.
