Definition: grape drop

Remove excess bunches, which corresponds to green harvesting. From the first days of summer, green grape pickers often pass through several times to reduce the number of bunches.

You had to be there in July and August, that's when you have to remove the grapes. In September, it is too late. However, this process should not be overused. If not enough bunches are left, the vine produces wood and vegetation. This is a problem for the future of the plant and future grapes. It was therefore necessary to regulate production so as not to produce too much in this vintage, but also to think about future vintages. Another drawback is that green harvesting is intended to reduce production in order to avoid dilution. However, if you try too hard, you can achieve the opposite effect: you cannot prevent the vine from compensating by producing larger grapes. This then creates a problem with the ratio of juice to skin. The skins contain phenols, which give wine its colour and tannins. With larger berries, there was a risk of producing wines with less substance; in other words, diluted wines.
Obviously, these practices are expensive. Paying people not to harvest seems absurd to those who are struggling to balance their budgets. And often they refuse to do so. Only estates that have a certain amount of cash flow and are assured of selling at a good price can embark on such an adventure. In other words, this type of vintage does nothing to reduce the social divide that increasingly separates the two worlds of Bordeaux: that of the grands crus and that of the petits crus, the entry-level appellations, or "favelas", as a Bordeaux wine merchant calls them.
Californian researchers debunk preconceived ideas (October 2007):
At the latest conference of the American Society for Enology and Viticulture, Californian researchers caused a stir by undermining viticultural practices "based on folklore rather than scientific research", as Michael Anderson of the University of Davis denounced. Commonly used cultivation techniques in vineyards were called into question. According to Anderson, thinning grapes before harvest to increase concentration is nothing more than a myth. The researcher conducted trials and found that regardless of the volume of fruit removed, there was no significant difference in the sugar concentration of the remaining grapes at harvest time. This finding also applies to early grape removal. "If you remove 40% of the grapes at veraison, it's even worse," says Anderson. Grapes from control vines that have kept all their grapes reach the same sugar concentration as grapes from vines that have been green harvested. Although there is a noticeable difference before ripening, this difference in density disappears once the grapes reach a potential alcohol content of 13% vol. Anderson admits, however, that there may be a difference in the aromas of the grapes, but in his opinion, this has no ultimate effect on the wines. "Is it worth dropping grapes?" Anderson asks. It should be noted, however, that these results are based on only one year of experimentation and need to be confirmed by further trials.
Another contested dogma is that irrigation deficit improves quality. It has been proven that early water deficit improves wine quality by reducing vegetation and berry size. However, many winegrowers remain convinced that water rationing until harvest, which reduces yields by dehydrating the berries, is also a factor in quality. Martin Mendez-Costabel of the University of Davis wrote his thesis on this subject. His conclusions: late-season irrigation affects yields but has little impact on the fruit or the composition of the wine. On the contrary, it allows the foliage to remain green, which continues photosynthesis. The berries therefore continue to enrich themselves with sugar and water. Late irrigation during berry ripening also reduces the pyrazine content, which is responsible for herbaceous flavours. His recommendation is to limit water supply to control vegetation and reduce berry size, then irrigate as soon as the berries reach a sugar content of 11% vol. This strategy limits yield losses without compromising quality.