Pros and Cons of Early Leaf Removal

In my previous post, I wrote about What is Early Leaf Removal? This is the follow up blogpost regarding the pros and cons of early leaf removal. Early Leaf Removal (ELR) is a technique that is still experimental and doesn't replace traditional canopy management activities but can be good for highly-fruitful varieties that produce a high number of clusters (3-4 per shoot) or large clusters such as Grüner Veltliner, Sangiovese, and Barbera.
The benefits of ELR are the following:

• ELR when performed at the onset of fruit-set, may induce a reduction in berry size and an increase in berry abscission due to carbohydrate limitation at the onset of fruit development
• ELR may be employed as a potential alternative to cluster thinning techniques used for crop yield control in highly-fruitful wine grape varieties
• ELR can be more easily mechanized, as opposed to cluster thinning for crop yield control
• ELR decreases cluster compactness by reducing the number of berries per cluster and/or the berry size and can serve to reduce the severity of Botrytis bunch rot infection in susceptible varieties
• ELR of basal leaves increases sunlight penetration and air movement in the fruiting zone, which is important for improving spray penetration within the canopy
• ELR can also reduce methoxypyrazines, ‘herbaceous’ aromas found in higher concentrations among immature grapes at harvest, and may contribute to improved wine color intensity in red varieties

Employing early leaf removal is tricky business because the basal leaves are being removed pre-bloom. During this time, the basal leaves are the one that are photosynthetically active, providing the carbohydrates to the inflorescence as well as the growing shoot.
The disadvantages of ELR may be:

• ELR may potentially exacerbate ‘poor’ fruit-set if extended periods of wet, cool (< 59°F), overcast, or very hot (> 90°F) weather conditions occur following leaf removal
• ELR may lead to bud damage as a result of physical damage during leaf removal and/or reduction of carbohydrate supply during bud development
• ELR effects on carbohydrate storage in perennial tissues and its relation to dormant tissue (buds and canes) cold hardiness development is still unknown and under active research at this time
• ELR use and crop estimation prediction is unknown at this time; cluster thinning is a more conservative approach and can provide a better estimation of final yield

Since we do not have overly fruitful varieties in our vineyard, with the exception of Barbera, which is still not producing any fruit, I think we will be sticking to the standard practice of leaf removal after berry set.
References:
1. Maria Smith and Dr. Michela Centinari, Early season grapevine canopy management, Part II: Early leaf removal (ELR), Dept. of Plant Science.
2. Tommaso Frioni, Shijian Zhuang, Alberto Palliotti, Paolo Sivilotti, Rachele Falchi, Paolo Sabbatini, "Leaf Removal and Cluster Thinning Efficiencies Are Highly Modulated by Environmental Conditions in Cool Climate Viticulture", Am J Enol Vitic., March 2017.