WHEN you combine heat, harsh light and ultraviolet radiation, people aren’t the only ones to cop sunburn.
Charles Sturt University is investigating how to reduce browning, cracking, shrivelling and the resulting financial losses in Orange’s wine grapes, which can affect up to 15 per cent of the crop.
Justin Jarrett’s higher altitude grapes suffered worse sunburn than his lower altitude grapes during last year’s heatwave and he knew he had a problem.
Mr Jarrett said sunburn created a “flabby” flavour in chardonnay grapes, while shiraz grapes started to taste like fruit cake.
“If you’re looking for a champagne base, you’re looking for that clear, crisp wine and so the flabby flavours that come from sunburn are not what we want,” he said.
“Sunburn has become more prevalent in the last four or five years – last year there was no sunburn at 700 metres, high sunburn at 900 metres and really it should be the other way around because it’s hotter at 700 metres.”
On a sensitive, mature chardonnay grape, symptoms can appear within five minutes once the berry reaches 40 degrees Celsius.
Mr Jarrett pruned leaves late, while others who pruned earlier suffered less damage.
CSU’s Dr Joanna Gambetta from the National Wine and Grape Industry Centre is conducting the research, testing three pruning methods – none at all, December at the end of flowering and mid-January.
“We’re trying to get guidelines to help farmers do it in the best way possible,” she said.
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