Malbec is a winegrape variety notorious for variable fruit set and, in Langhorne Creek, bunch collapse after heat events often occurs, which can reduce yield even further. Likewise, Cabernet Sauvignon appears to exhibit bunch necrosis after sudden, transient heat events, even though the vine canopy appears relatively robust.
Extreme weather events are likely to increase in frequency under a changing climate, and heatwaves within otherwise relatively normal or mild seasons have increased notably in the region over the past five years.
There is some local evidence that simply saturating the root zone with irrigation to mitigate heat impacts is not the solution. Growers who have had success with managing Malbec through high heat have employed overhead low-emission sprinkler or mister infrastructure with an aim to maintain canopy temperatures below 36 degrees Celsius.
There is a desire to understand the physiological factors which contribute to these impacts, hopefully leading to means of better managing vines through heat events.
Why is it important?
Malbec is an important high value niche variety in Langhorne Creek, but its unreliable nature is making it unviable for many to continue growing. In vintage 2019 Malbec represented 2% of the region’s crush and value from an equal percentage of the total vineyard area of the GI (SA Wine Grape Crush Survey 2019). There is demand for the fruit, however growers are increasingly facing hard business decisions around continuing to grow Malbec or remove/rework blocks.
Cabernet Sauvignon (alongside Shiraz) is one of the mainstays of the region. It represents 30% of the total vineyard area of the GI, and equally approximately 30% of the volume and value of the annual crush in a regular year (SA Wine Grape Crush Survey 2019). However, Cabernet Sauvignon is now not considered the no-fuss, reliable producer it once was in the region.
What would success look like?
Strategies, benefits, and limitations for best practice management of Merlot and Cabernet Sauvignon during extreme heat events in Langhorne Creek.
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Lian Jaensch: firstname.lastname@example.org