Dangerous Weather in the Vineyard (II)

The effects of climate change intensify common weather disturbances that pose a significant threat to farming in general and vineyards in particular.

Hailstorms are among the most destructive. They can occur early or late in the season and affect the grapevine at any point in its growth cycle.

Early and late-season hailstorms: how they affect the vineyard

In particularly exposed areas, hail can cause significant damage, especially after budbreak (early March). The consequences for the vine vary, depending on the time of year and the growth stage of the plant.

Early-season hailstorms occur between late December and March. This period includes budbreak and bloom.

• Hail can break off young shoots, producing a cut in the node that can potentially affect the entirety of the plant's vegetative organs.

• Hail can shred leaves and shoots and seriously damage inflorescences.

• After the hailstorm, the plant's healthy secondary buds will produce new growth, but this “second generation” will see a two to four week delay in phenological ripeness. In addition, the new foliage is more susceptible to fungal infections.

• Damaged inflorescences and the lower fertility of secondary buds can diminish crop size and quality. Berry variability in the clusters and delayed vegetative growth can impact quality.

The effects of late-season hailstorms (between April and October) are equally dangerous for the harvest and the plant's health, because in the worst case scenario, they threaten the perennial nature of the vine.

• Defoliation: A reduction in leaf surface area has a negative impact on fruit maturation and shoot maturation, especially in long-cycle varieties.

• Injured vine shoots: Damage to canes and their buds can lead to pruning problems and harm the following year's crop production. When the wood is severely damaged in two or three-year-old vines, it is best to retrain them, which means a loss in crop production of one or two years.

• Damaged clusters: At worst, heavy hailstorms can destroy an entire crop and even affect the following year's harvest.

Much like after an early-season hailstorm, the leaves and shoots grow back, but this second generation may suffer stunted growth and poor shoot maturation, which can complicate dormant pruning.

The injured shoots and clusters are susceptible to the dreaded “white rot,” a disease that causes pale, irregularly-shaped, concentric blotches to appear on the grapes, covered in small lesions. Eventually, it desiccates the fruit.

The search for solutions

At this point, technology is not advanced enough to establish prevention protocols that could impede the formation of ice crystals with any degree of success.

For the science buffs: the only scientifically based method, known as cloud seeding, manipulates the ice cores by introducing silver iodide into the hail-bearing cloud. However, no promising results have been replicated so far.

So what should one do? First of all, get a good insurance policy. Then cover the vineyard lots with anti-hail nets. This is the most effective method, albeit not the most practical given its high installation and maintenance costs. However, it does pay off when the nets protect top-quality grapes, which we use to make our best wines.

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Anti-hail nets installed at the Torres Family's vineyards in Tremp (foothills of the Pyrenees).

Although we use satellite weather forecasting systems and other modern technology, we are very proud of the fact that our people still go out to the vineyard and look at the sky every morning, interpreting every sign, intuitively sensing the most minute change. What it ultimately comes down to is a combination of science and human experience.