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A man checks on vine buds as anti-frost candles burn on a vineyard in Le Landreau, France, on April 12, 2021.AFP Contributor#AFP/AFP/Getty Images

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Most wine regions in France and Italy have been hit by severe frosts that threatened this year’s harvest. Spring frost is a big risk for wine regions, where it can severely damage the newly emerging buds and shoots. This year’s is being called the worst in decades.

France’s agriculture minister Julien Denormandie said the frost was “an episode of extreme violence that has caused very significant damage.”

A sudden cold snap came after a period of mild weather that spurred vines to produce their first green shoots, which are vulnerable to the cold. Industry estimates suggest 80 per cent of French vineyards have been affected, with forecasts continuing to call for cold overnight temperatures in northern regions. Regions spanning from the north to the centre of Italy were hit by frost damage due to last week’s exceptionally cold nights.

Frost rarely affects vineyards equally, so some vines might have only suffered minor damage. Others may face the loss of their entire crop. Not all grape varieties are equally susceptible to chilly conditions, and susceptibility depends on bud-development stages.

Social media posts earlier in the week show mobilized efforts to protect vineyards and their tender new growth from frigid temperatures. Lighting fires or candles near vines or free trees to produce enough heat to prevent frost pockets from settling is a long-standing technique used in early spring. But systematically placing and lighting these fires takes time and labour, which means that the best vineyard plots are a priority.

Fans or wind machines that keep cool air moving are commonplace in Niagara vineyards. Because frost is a constant threat throughout the year, wind machines have replaced an earlier practice of hiring helicopters to hover over vineyards for air movement. Vineyards in Germany, the Loire Valley and other European regions still call upon helicopters on an as-needed basis.

In the Okanagan and other regions, sprinklers are used to create a layer of ice to insulate the tender buds from the cold. The small amount of heat created as water changes from liquid to solid can raise the temperature around grapevine buds and shoots. A large amount of water is needed for a steady supply to coat buds and shoots to release heat and rise the temperature.

Growers and winemakers will need to see how the buds react in the coming days to gauge the extent of the damage. The threat of frost will be a concern in cooler-climate regions until the end of May.

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