The severe heat and a burning wind, with temperatures measuring up to 48°C around Clanwilliam, Trawal and towards Vredendal almost two weeks ago, has had its most noticeable impact on the Red Globe, a cultivar known to be susceptible to sunburn.Preliminary estimates of the damage range from manageable to 90%, even a total loss of Red Globe on some farms. In some places a mere two hours at this temperature, with wind, was enough to nearly wipe out this season’s Red Globe harvest. Most damage occurred in the Olifants River region, but there have also been reports of Red Globe sunburn in the Berg River region. The cultivar does well in these areas, where it’s more present than in other areas.
Some growers have ruefully noted that the Red Globe season had, until the heat came, been looking really good. “This isn’t pleasant to see, these grapes were looking beautiful, we were looking at 7,000 cartons a hectare,” sighs a grower on a grape farm in Trawal. “At least on our farm the damage is mostly limited to the vines at the ends. Those at the centre of the vineyard were more protected against the scorching wind that came through here.”
Due to the critical drought, growers in these areas largely employ drip irrigation which keeps the soil moist at root level, but has no effect on ambient temperatures. In hot areas with plentiful water where micro irrigation is in place, above-ground temperatures are also cooled down and the extent of heat damage can be limited.
Extra-large berries lose size
Another effect of the heat manifests on berry size: the Martian temperatures have reduced extra-large berries to large. That seems to be a theme of the South African grape season thus far: difficulty in optimising berry size, as noted in SATGI’s crop estimate adjustment of last week.
Growers in the Olifants River region note that Crimson and Autumn Royal, which were also at the hard, green berry stage, showed no damage after the heat. Damage is also reported on Allison (Sheegene 20) and Ralli.
According to the South Africa Table Grape Industry organisation, Red Globe, still among the top ten vines planted in the industry, covers just over 800ha countrywide, the majority older than 16 years. It used to be a more dominant cultivar in the South African industry, ranking first in terms of production volumes during 2006/7 and third over the past season in export volumes. Currently red seeded varieties make up just 7% of the basket.