Heavy downpours, hail and flash floods have caused some damage across the Western Cape over the past few days. Although it has resulted in sporadic damage on some wine farms, experts say it is nothing that cannot be corrected with effective spraying programmes and canopy management practices.
According to SA’s wine industry body Vinpro, heavy dew over the wine-growing areas in the Western Cape ranged from 79mm in the Paarl to 28mm outside Darling. Despite causing some damage to wine farms, the rainfall comes after a very dry winter and spring, which led to lower groundwater levels than normal.
Conrad Schutte, Vinpro consultation services manager, said producers had to start irrigating earlier and more often than usual to meet the needs of vineyards.
“More frequent load shedding has an enormous impact on irrigation schedules where producers, especially in intensive irrigation areas, cannot irrigate enough to meet the vineyard’s needs.”
In the province, vines are currently in their cell division phase, specifically berries. In this process any stress, especially water stress, will have an undesirable impact.
According to Vinpro, this results in smaller berry sizes with a corresponding reduction in the total tonnes per hectare recovered. Which is why the rainfall of the last few days is extremely welcome for replenishing groundwater, relieving pressure on irrigation schedules, and encouraging berry growth and crop sizes, Schutte said.
“Dam levels will also rise after the good rains, which is beneficial for irrigation during the rest of the season,” he added.
Look out for diseases
There are, however, risks associated with above-normal rainfall seen in various parts of the province.
According to Schutte, the heavy rain increases the occurrence of fungal diseases due to the increased prevalence of free water, as well as the higher humidity and temperature.
“The weather conditions of the past few days with rain showers followed by hot, humid conditions, were favourable for the primary and secondary infection of especially powdery and downy mildew on vineyards,” said Schutte.
What can farmers do?
So what can farmers do to protect their vineyards?
Schutte explained it is normal for producers to follow preventive fungicide spray programmes, but they need to apply follow-up sprays. This should happen after the rains have subsided as they are able to gain access to the vineyards
“However, the risk of infection while berries and bunches are drying has increased, and the effects of this and the effectiveness of spraying programmes can only be evaluated in a few weeks,” Schutte pointed out.
In some cases canopies and bunches have been damaged in Paarl, Worcester and Robertson due to random hailstorms. However, it is still early in the growing season for any significant damage to occur.
Damaged grapes on bunches should dry up if treated effectively, with minimal negative effects on total crop size.
“The rain will stimulate the vines’ vegetative growth where it is still actively growing,” said Schutte.
“In these cases, canopy management practices must be applied to limit shoot growth. Fruit zones can be cleared with leaf breaking for effective lighting and air movement. This will benefit ripening and help control fungal diseases.”
Meanwhile, Vinpro reports that damage to vineyard roads, buildings and infrastructure have also been reported and are being repaired.
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