3.1.5.a Is the Botrytis cinerea fungus present?

Overview

Defining a harvest order depends not only on tastings and/or chemical analyses, but also on careful monitoring of the vineyard's overall health throughout the ripening process. The plot harvesting order when overall health is good is unlikely to be modified or only slightly since there is no major risk that could alter grape quality. In this case, tastings and analyses are sufficient to determine a suitable date to harvest and guarantee an optimal qualitative potential. However, in the event that there are threats to the vineyard's health, the harvest date must be brought forward, in order to limit the risk of qualitative and quantitative loss of the grapes.

Botrytis cinerea (Fungal disease management) is a fungus that colonizes the vine's herbaceous organs as well as the bunches and causes symptoms that appear similar to grey rot and peduncle rot. Risks are highest from the véraison onwards because of the humidity and temperatures around 20°C.

Were there any vine moth contaminations during the season?

The first generations of Eudemis and Cochylis (Grape caterpillars) form glomeruli (white webs of silky threads) on the inflorescences and/or on the bunches. The following generations attack the berries by piercing their skin. The caterpillars are also vectors of Botrytis, they carry the fungus on their hairs or inside their digestive tracts. The first generation can be present as early as flowering when they form their glomeruli. Even if the weather conditions are unfavourable to Botrytis at this phenological stage (and it remains in latent form), it is possible to combat the reproduction of these moths from this point onwards. Botrytis risks are also increased by the caterpillars' oviposition which pierces the film and makes the sugar ooze out, thereby forming a new entry point for the fungus.

Other contamination factors

Grape caterpillars are not the only contamination risk for Botrytis on grapevines. The fungus develops when the bunches' microclimate is humid and warm (the fungus' progression starts at temperatures above 13°C, and is very fast around 25°C) and/or when the herbaceous organs have been damaged. Prophylactic measures can be put in place very early (in spring) in order to avoid any early development of the fungus which is latent until the berries are receptive. Botrytis_ can then become enclosed at the bunch closure stage and cause serious damage to berries that will be invisible because they are hidden within the cluster. Early leaf removal is a good example of prophylactic control
Green pruning.

A criterion for early harvesting?

Increased development of Botrytis cinerea may lead to an earlier harvest date for the plot. Peduncle rot leads to withering of the berries and often their fall before the harvest. In order to avoid a massive loss of yield and quality, the initially planned harvest date can be drastically advanced. Grey rot, on the other hand, affects the berries rather than the stalks, forming downy efflorescences. The damage caused by Botrytis is considerable as it causes a quantitative loss when the affected berries burst and juice is lost, as well as a deterioration in the quality potential of the affected grapes. Botrytis, when it gets into the vat, can cause a partial oxidation of the must. The laccase oxidizes the polyphenols. This enzyme can also cause problems with fermentation (alcoholic and malolactic) and clarification issues. Laccase tests by colorimetry or enzymatic analysis are relatively quick to quantify its content and its probable impact on the wine.