A nerve-wracking season 10 November 2006

Untimely Cape rains cause problems in the vineyards, winegrowers tell Angela Lloyd

In his presentation on global warming at the recent Wines of South Africa/Winetech Changing Environments Seminar, Professor Hans Schultz spoke about an increase in the frequency of extreme weather scenarios as part of predicted climatic changes for most wine growing areas of the world.

If not extreme, the unseasonably cold, wet and windy spell with occasional thunderstorms last week interrupted what had appeared a smoothish spring ride once winter departed abruptly at the end of August. The vines were already well into their growing stride, some were flowering or already through this phase; this wasn't the sort of weather those tender shoots with their nascent bunches wanted or required.

We asked a few wine growers what degree of damage, if any had been inflicted on their vines and for a prognosis as the growing season progresses. 

In Elgin, Paul Cluver's winemaker,  Andries Burger, reports lost shoots especially on young vines going onto the wire. Klein Constantia's Adam Mason says they have also lost a shoot per vine on some of their top sauvignon blocks, though this was caused by an earlier, October westerly. Damage caused by last week's rain (around 50-60 mls), wind ‘and a short burst of hail that lasted a few minutes' has yet to be quantified. Mason's Murphy's law moment arrived just as the vineyard team finished an antifungal spray last Friday when the heavens opened – a situation, he compares with the motoring enthusiast hearing the thunder roll as he buffs the last spots of polish off the convertible!

Whims of the wind
The Delheim vineyards on the Simonsberg are, like those at Klein Constantia, pretty exposed to the whims of the wind, except it's usually the south easter that causes damage. Victor Sperling, the farm's viticulturist, says that along with last week's gales, which hurt the sauvignon blanc in particular, they recorded 80 mm of rain, an amount he suggests, ‘that was really too much for this time of year.'

Further afield in Tulbagh, Chris Mullineux from Tulbagh Mountain Vineyards has been glad of ‘good winds – good meaning they have dried the vineyards out after each bout of rain, but not really strong enough to damage the vines, apart from some light tipping and topping.' The ‘rain' he refers to is not just last week's downpour, but `.. nine meaningful bouts – 10 to 30 ml each – since budding at the end of September.' So much for the Cape winelands enjoying similar weather patterns!

Mildew
If losing shoots is one inevitability, mildew must be another high on the list after such damp conditions. The serious downy mildew problems encountered in 2002 are still fresh in winegrowers' minds, they don't want to be caught short again. Both Burger and Sperling confirm they have been spraying late into the night – Burger on Sundays too – to prevent mildew. Mullineux, who farms organically, tries to do without spraying (or only limited amounts of copper and sulphur), so is glad of the drying winds after the rain that have chased off mildew, though he admits having to be super vigilant, on top of canopy management and concerned at the ‘pretty nerve wracking season.'

But not everyone believes last week's conditions were conducive to mildew. Vilafonté's Phil Freese spoke to a chemical rep, who, Freese says, doesn't have big guns to knock down later infections, so is taking a soft approach. The rep and others confirm that conditions have not had the kind of moisture and temperatures required for downy mildew infections. 'Cooler temps have been one of the favouring factors even though we have been wet', Freese explains. Hopefully this information is correct, as Freese confirms a downy infection at flowering can wipe out the flowers and berries in a day or so..

Rampant greenery
Rain brings growth, of course, and this appears to be winegrowers' biggest headache, demanding the most future effort. ‘I have a feeling we are going to have our hands full over the coming weeks managing rampant canopy growth as a result of the additional nitrogen and water due to the rain and lightning,' sighs Adam Mason, echoing the fears of his colleagues.

Hartenberg's Carl Schultz points out another consequence of the recent downpour. ‘The ability to naturally manipulate the vine to produce smaller berries has been significantly reduced on the early red varieties, like pinotage and pinot noir. Ideally we would like to apply controlled water stress from set to veraison as this period determines number and sizes of cells. Consequently the less moisture the smaller the berries.'

He nevertheless remains positive, recognising that `bleeding' off juice can be applied at the start of vinification. And he welcomes the rain ‘as it will reduce the need for later supplementary irrigation to ripen the crop from veraison onwards if conditions remain hot and dry.'  Sperling also mentions that with the drier weather unusually high insect activity may be anticipated.

What this all means for the 2007 harvest – still around two months away – it's too early to say, especially with many varieties still to go through flowering and the unknown weather factor at that time, though Sperling is pretty certain the above average crop anticipated on some varieties due to flower last week will have been reduced.

As I write this, a 60% chance of rain is forecast for next Monday evening – out with the spray trucks again, guys!