What solutions are there against spring frost in vineyards?

Every year, spring frosts represent a dreaded threat to vineyards. Unlike winter frosts, which affect a dormant vine, spring frosts strike when the plant restarts its growth cycle. A sudden drop in temperatures is enough to destroy young buds, considerably reduce yields and jeopardize the economic balance of wine-growing operations. Faced with this phenomenon, winegrowers have several strategies, in anticipation and active protection methods. At Agrobiotop, an expert in agrobiology, we develop natural solutions to deal with this problem. Explanations.

Frost and its impact on the vine

Spring frost results from a sudden drop in temperature below freezing, often accentuated by clear skies and a lack of wind. The further along the vine is in its cycle, the more vulnerable it becomes. Two types of frost are particularly feared.

• White frosts : they fluctuate between -3 and -5 °C, and are formed by nocturnal radiation. The cold air accumulates on the ground, creating a thin film of ice on the vegetation. These episodes are frequent in the lower hillsides and valleys where the cold air stagnates.
• Black frosts : these are caused by the arrival of cold, dry air masses, with temperatures that can drop to -9°C. Unlike white frosts, they are not accompanied by the formation of ice, but their drying action causes even more severe damage to the vine.

Spring frost damage to vines

From the first hours following a frost episode, the damage is visible: the affected buds turn brown and eventually dry out. On the vine shoots, impaired sap circulation is manifested by a brown or grayish phloem , announcing wilting and progressive drying out of the branches.

This destruction of buds has a direct effect on the harvest. When a primary bud is affected, the vine can produce a secondary bud, but this generally gives a less abundant and later harvest. A frost occurring at an advanced stage of development leads to heterogeneity in the maturity of the grapes, making winemaking more complex.

The economic impact is considerable. In April 2021, a spring frost caused wine production to fall by 25% compared to the average of the previous five years. A reduced harvest means a reduced wine supply, influencing market prices and increasing dependence on foreign imports.

How to anticipate and combat frost?

Strategic choice from planting

The resistance of a vineyard to frost begins well before the first leaves appear. The choice of the plot plays a decisive role: avoiding valley bottoms and areas where cold air stagnates helps to limit the risks. 

The presence of hedges or dense woodlands can also promote the accumulation of cold air and should be taken into account.

Some grape varieties are more frost resistant than others. Choosing varieties with late bud burst reduces exposure to early frosts. 

Furthermore, delaying pruning the vine allows the appearance of buds to be delayed, thus reducing the risk of destruction by frost.

Direct protection measures

Faced with an announced frost episode, several methods can be put in place to protect the vines.

• Water spraying : This technique involves spraying water on the buds continuously throughout the frost period. As the water freezes, it releases latent heat, thus maintaining the temperature of the buds close to 0 °C. Although effective, this method requires a large amount of water and can only be used in regions where the resource is abundant.
• Vineyard heating : Using candles or heaters can warm the air on the ground. However, this solution is expensive, requires a lot of labor and becomes ineffective when temperatures drop below -5 °C.
• Air mixing : Wind turbines and helicopters are used to mix cold stagnant air with warmer air layers higher up. This technique can provide a temperature gain of 1 to 4 °C, but its high cost limits its use to farms with a large budget.
• Heating cables : fixed to the trellis wires, they directly heat the buds. Although this method represents a significant initial investment, it offers localized protection with a reduced environmental impact.

AGROBIOTOP solutions against spring frost on vines

We manufacture effective natural solutions and biostimulants against spring frost phenomena in vineyards:

• Bentobio : application 24 to 48 hours before frost. Dusting or foliar spraying. Aeration, decompaction of soils, avoiding water stagnation.
• SILIBOOST
• YAKADOP
• YAKAPRO
• CHITOPROTECT

What to do after a spring frost?

Once the frost has passed, it is essential to accurately assess the damage before taking any corrective action. Careful observation of the buds will allow you to estimate the crop loss. However, it is recommended to wait two to three weeks, as some lesions are not immediately visible.

If less than 40% of the buds are affected, the vine will be able to naturally compensate for the loss thanks to secondary buds. Between 40 and 60% damage, production will be reduced and care will have to be increased to preserve the pruning wood. When more than 60% of the buds are destroyed, the priority will be to reform the vine by promoting the development of healthy branches.

Providing the right nutrients will help the vine recover more quickly. It is advisable to wait for the vegetative recovery before providing nitrogen, in order to avoid too rapid development of the still weakened tissues. Monitoring diseases also becomes essential, because a weakened vine is more susceptible to attacks by fungi such as mildew and powdery mildew.

Finally, winegrowers must consider solutions to limit the financial impact of frost episodes. Taking out crop insurance is an effective lever to compensate for losses. However, even today, only 50% of winegrowers opt for this protection, and less than 30% in certain winegrowing regions such as Bordeaux. With the increase in extreme weather events, this precaution could become a key element in the sustainability of farms.

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