Riverina heatwave may cause grapes to shrivel and wine production to stall

Tim McMullen surveys the Chardonnay crops at Borambola Wines ahead of a second week above 40-degrees. Picture: Emma Hillier
Tim McMullen surveys the Chardonnay crops at Borambola Wines ahead of a second week above 40-degrees. Picture: Emma Hillier

Soaring temperatures across the nation have caused enormous problems for wine producers.

Vineyards in South Australia,  Victoria, and the NSW Hunter Valley have already registered catastrophic crop failures owing to grape shrivel and sunburn. 

With mere weeks until harvest, the Riverina’s current heatwave is causing some concerns for its local producers.

“At this point, it’s a bit too early to tell what the outcomes of the season will be,” said Tim McMullen, managing director of Borambola Wines.

“Each year has been coming in earlier. We’d normally harvest [for] Chardonnay in late February, but last year we were harvesting in the first week of February.”

This week represents the second in a series of heatwaves forecast for the Riverina. 

Wagga is expected to reach temperatures in the mid-40s by the end of the week. Following from a dry winter, the anticipated heat swell may cause the fruit to develop prematurely.

Anything above 35-degrees is potentially treacherous for grapes, especially at this time in the season.

“When it gets so hot, the vines just shut down and don’t do anything,” Mr McMullen said.

“All you can do is pump a lot of water onto them and hope the weather cools down.”

With temperatures in Wagga expected to drop to the mid-30s at the weekend, Mr McMullen is confident the crop will weather through.

“[The vines] can recover if you get some cooler weather. The week after [this week] is showing a bit of compassion,” he said.

Nevertheless, the heat’s intensity may still make for a strange season.

“In higher temperatures, the sugars come in early,” said Mr McMullen.

“But it’s not just the sugars, you also have to balance the taste and the colour. 

“You don’t want one coming in ahead of the other.”

Labelled as the Baume reading, the sugars determine the alcohol concentration in the eventual product. 

Overly ripe grapes make for higher alcohol content.

“So we’re having to be extra careful, going around the vineyard and taking a bunch of samples to measure the sugar levels,” said Mr McMullen.

Harvest generally begins when the Baume level reaches 12 Brix.

“I’m expecting the Baume will be well ahead of what it usually is,” said Mr McMullen. 

“It increases one Brix per week so if it’s about nine Brix this week, it’ll only be two weeks before we’ll have to start harvesting.”