Frost is enemy number 1 for winegrowers. As soon as the first buds appear, devastating frosts are feared.
The future clusters of grapes are laden with water and particularly sensitive to cold spells, even short-lived ones: the thermometer only has to drop below -2 degrees overnight to destroy them. Plots located in dips are the most vulnerable. Icy air can accumulate there for several days, transforming the morning dew into fatal ice.
In the vineyards, the damage is plain for all to see. Once affected, the buds turn black hence the term black frost. To avoid sacrificing a large chunk of their crop, winegrowers increasingly intervene, as soon as the first reports of alarming weather are issued. In regions like Touraine and Burgundy, they no longer hesitate to use helicopters, which take off at first light. With their blades rotating at high speeds, the machines create wind that dries the air while warming the atmosphere. Experimented for the first time in 2017, the method proved effective despite its high cost of around 200 euros per hectare. However, the initial investment remains lower for winegrowers, unlike wind machines which, although they have proved their effectiveness, are prohibitively expensive for the vast majority of vineyards.
Other natural elements also help to combat frost. Fire is a case in point and helps boost the temperature by a few degrees thanks to the smoke which curls between the vine rows. Fireboxes then have to be deployed across the vineyard, in the form of candles, propane burners or heaters. More surprisingly, water can also be an ally in the event of frost. Sprayed on the buds, it forms a natural shell around the plants, thus protecting their core. The only drawback is that it requires expensive equipment, forcing winegrowers to choose between different plots.
By Alexandra Reveillon