Leaf remover
Leaf removal involves removing some or all of the leaves from the vine in the fruiting zone. The definition is simple, but the optimal conditions for carrying out the process are difficult to control. To achieve high-quality leaf removal, it is essential to understand and adhere to several criteria. When carried out manually, leaf removal from vines is labour-intensive and consequently incurs very high costs. Mechanising leaf removal is therefore a cost-effective operation and enables a high work rate whilst ensuring the integrity of the grapes, thanks to the settings and design of the leaf-removal machines.
Why do we thin out the vine?
Just a few years ago, leaf removal was a very popular technique as it allowed grapes to ripen more quickly through direct exposure to the sun or helped to limit the development of Botrytis cinerea on high-yield plots. But over the last ten years or so, practices have changed…
Global warming and increasingly hot, dry summers mean that leaf removal – whether manual or mechanical – is becoming less and less common. In fact, the focus is now more on protecting the bunches from the sun than the other way round.However, there are still reasons to prune the vines; here are the most common cases:
Global warming and increasingly hot, dry summers mean that leaf removal – whether manual or mechanical – is becoming less and less common. In fact, the focus is now more on protecting the bunches from the sun than the other way round.However, there are still reasons to prune the vines; here are the most common cases:
- Vines with vigorous growth that are susceptible to rot
- Optimising vine treatments by improving the penetration of plant protection products into the fruiting zone
- Saving time during manual grape harvesting
Vineyard with leaves removed by machineImproving public health
Removing the leaves reduces the build-up of foliage around the bunches, which then benefit from better ventilation. The grapes dry more quickly. This reduces the risk of fungal diseases developing in vulnerable grape varieties and in high-risk years, such as grey rot and mildew…The bunches are more accessible, facilitating the penetration of treatment products during localised applications. This can help improve the effectiveness of treatments applied to the bunches.
Improving the quality of the harvest
As the leaves that provide shade are removed, the grapes are more exposed to the sun and heat. This results in improved synthesis of phenolic compounds and aromas. When leaf removal is carried out correctly, red wines are more tannic and white wines more aromatic. However, excessively high temperatures around the bunches can have a negative impact on aroma production. It is important to retain sufficient leaf area so as not to limit the sugar concentration in the grapes.Saving time during the grape harvest
In the case of manual harvesting, leaf removal shortly before the harvest helps to increase the pickers' output by exposing the bunches. Carried out mechanically on both sides of the rows 24 to 48 hours before harvesting, its aim is to remove as many leaves as possible. Harvesting time is reduced by 30 to 50 per cent on vines that have been mechanically defoliated. This leaf removal must not be carried out too early, so as not to hinder the final ripening of the grapes and to avoid the risk of grey mould caused by any damage to the berries.How do you thin out the vines?
Which plots should be thinned?
Those with excessive foliage, which hinders the proper ripening of the grapes and allows a microclimate favourable to the development of diseases to persist.Certain grape varieties are more susceptible to disease than others and should be thinned out as a priority.The fruiting zone must be clearly defined. To achieve this, the trellising must be impeccable, as irregularities in the canopy structure may lead to an increase in damage.
This is why the characteristics of each region (training system, climate, grape varieties, etc.) must be taken into account in order to determine the optimal leaf-thinning method for each individual vineyard.Leaf removal must not be too severe. Priority should be given to removing leaves from only one side of the row, particularly the side facing the rising sun. This helps to minimise the risk of sunscald, on the one hand, and promotes the effective drying of dew, on the other.
Should you separate the leaves by hand or by machine?
The choice of method involves a number of criteria, both qualitative and economic. Manual leaf removal is much more expensive but produces a more meticulous result and ensures that all the leaves in front of the bunches are removed. Machines are faster and allow a tractor driver to defoliate around 5 ha per working day. The new models have significantly reduced the rate of damage to the bunches.When should you thin out the vine?
Leaf removal can be carried out from the end of flowering/fruit set in the vine until the day before the harvest, depending on the desired outcome.Trials carried out by the IFV show that early leaf removal is preferable for the following reasons:- better results in controlling grey mould
- gradual exposure of the bunches and partial coverage by the inner shoots to minimise the risk of sunscald
- higher polyphenol content in vines where leaf removal is carried out early
Feed source for mechanical leaf-removing machines
Hydraulic power supply
Certaines fonctions de l'effeuilleuse pouvent nécessiter une source hydraulique, tels :- l'entraînement de l'hélice du ventilateur ou de la turbine
- les manoeuvres de hauteur, de largeur, d'inclinaison
- le pivotement de la tête d'effeuillage
Pour cela, deux solutions :
- Soit vous utiliser le circuit hydraulique de votre tracteur car la pompe interne est suffisamment puissante, en bon état et à un débit en huile (L/min) suffisant (voir avec la demande en huile de l'effeuilleuse concernée ou tout autre matériel).
- Soit vous vous équipez d'une centrale hydraulique externe pour avoir un circuit d'huile indépendant de votre tracteur. Cette centrale hydraulique est entrainée par la prise de force de votre tracteur et assure un débit d'huile adaptable à votre outil.
Cette deuxième solution est la plus adaptée car elle peut se monter sur tous les tracteurs (vieux et récents) et peut servir pour d'autres matériels (épampreuse, intercep) sans solliciter et user votre circuit et pompe hydraulique de votre tracteur.
Power supply via the power take-off
The power take-off can be used to drive the turbine, to drive an independent hydraulic unit or to operate the compressor in the case of pneumatic leaf-removing machines.The tractor must have sufficient minimum engine power (specified in cv and kW).
Leaf removers are designed to operate at an engine speed of 540 rpm. Some manufacturers adjust the power take-off to vary the turbine's rotational speed and thus the suction power.
Coupling system
Leaf-stripping machines can be mounted on a row-crop tractor (with a standard rear hitch or at the front on the weight carrier) or on a straddle tractor.Swivelling of the leaf-removal head
The swivelling of the leaf-removal head is an important feature of single-head leaf removers when removing leaves from one side only. It allows the head to be moved to the other side when changing rows. This manoeuvre is carried out by a hydraulic or electric cylinder.Principles of adjustment
Position the leaf-removal head at the fruit-bearing area
These are the height adjustments that allow the leaf remover to be adapted to the trellis height and the width of the rows. These adjustments are made on the frame of the leaf remover or the straddle frame. They are often operated by either hydraulic or electric cylinders.
Thinning of the fruit-bearing area
Influencing the defoliation rate
The following diagram summarises the various adjustment options that affect the defoliation rate.
(1) - Tractor forward speed
(2) – Rotation or translation of the protective grille
Rotation about the central axis of the entire defoliator head in the case of defoliators with two fans
(3) – Pressure exerted by the leaf-stripping head on the vegetation (contact force)
(4) – Horizontal angle of attack between the defoliator head and the trellis
(5) – Vertical angle of attack (or inclination) between the defoliator head and the trellis
(6) – Distance between the sensor and the grid
Distance between the blade and the grid
Adjustment to row width
(7) – Air pressure or vacuum applied to the foliage and rotational speed of the air jets in the case of pneumatic leaf-stripping machines
(2) – Rotation or translation of the protective grille
Rotation about the central axis of the entire defoliator head in the case of defoliators with two fans
(3) – Pressure exerted by the leaf-stripping head on the vegetation (contact force)
(4) – Horizontal angle of attack between the defoliator head and the trellis
(5) – Vertical angle of attack (or inclination) between the defoliator head and the trellis
(6) – Distance between the sensor and the grid
Distance between the blade and the grid
Adjustment to row width
(7) – Air pressure or vacuum applied to the foliage and rotational speed of the air jets in the case of pneumatic leaf-stripping machines
(5)
(2)
(3)
(2)
(6)
Experiment
See the list of experimentsSee more 
