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New Zealand - Fans get to work as spring frosts threaten precious grapes

Vineyard frost fans have been doing their bit to protect one of Marlborough’s biggest money spinners after a few cold starts in October.

The fans, which pull warm air down onto the vines, are used when grapes start to bud – as a spring frost can lead to crop loss.

Blenheim experienced four frosts in the first week of October, while all of October 2018 had only two frosts.

But Marlborough Plant and Food research scientist Rob Agnew suspected frost fans would have been used more out in the Wairau Valley because of its colder climate.

Villa Maria viticulturist Stuart Dudley said because Marlborough was a cool climate viticulture region there were definitely areas that were exposed to spring and autumn frosts.

“The fans work by effectively bringing down warmer air,” Dudley said.

“It’s called an inversion layer, effectively it’s the same principle that is used by helicopters to protect the crops, but wind machines are a lot more reliable.

“For us, as viticulturists, the wind machines are great, because if you get a forecast saying it might get to zero [degrees Celsius] and then you would have to toss up whether to spend the money on helicopters or not, whereas if you’ve got a frost fan the decision is already made, you just have to flick it on.”

Most were automatic, with a start temperature just above zero, but some grapegrowers had started switching from two-bladed fans to four or five, which were quieter, Dudley said.

A Neighbourly poll showed 50 per cent of respondents who lived next to a vineyard were used to the sound.

However, 17.3 per cent of respondents said they struggled to sleep at night because of the sound.

Hawkesbury resident Nigel Taylor said noise from frost fans was something “you get used to”.

“You hear the two-bladed ones more than those with four or five,” Taylor said.

“You can definitely hear them but they don’t interrupt us, you learn to live with it.

“They’re temperature-controlled so you notice when they turn off too, it’s not a major disruption.”

Jenny King said rural residents knew living next to a vineyard could come with some noisy nights.

“It’s a small price to pay,” King said.

“It doesn’t make for a great mood the next day but it’s one of those things.”

King said she tended to hear the helicopter from the cherry orchards in Springlands more.

Marlborough resident Ben Wallace said the fans were “minimally disruptive”.

“The benefits of frost fans for the local economy far outweigh the noise you have to put up with,” he said.

Source – https://www.stuff.co.nz