The Botrytis cinerea
During the colonization of the grapes by Botrytis cinerea , the appearance of the berries changes. They will go from the “gold” stage to the “fully rotten” stage then to the “roasted rotten” stage.
"Fully rotten" stage
("pourri plein" in French)
At this stage, Botrytis cinerea develops under the skin of the berries, giving them a purple-brown
color.
The colonized berries keep their initial volume and are dotted by branching tree-like brown spots (conidia).
"Roasted rotten" stage
("pourri rôti" in French)
The hot and sunny afternoons bring about an evaporation of water through the skins made permeable by Botrytis cinerea’s enzymes.
This evaporation of water causes the concentration of sugar to increase and gives the berries a wrinkled, candied appearance with a purple-brown color (like a raisin).
In addition, Botrytis cinerea colonizes clusters heterogeneously. Therefore, a single cluster may present all of the different stages of the fungus’ evolution: speckled, fully rotten and roasted.
Finally, other molds are waiting for the slightest weakness of Botrytis cinerea to replace it and irreparably spoil the grapes.
All these parameters force the harvest to take place only by hand in various passes every one to two weeks – mechanical harvest is strictly forbidden in the Monbazillac appellation. This allows KALIAN to harvest only the portions of the cluster that are affected by the fungus.