Grape pruning trials prove fruitful

03:14, Jun 17 2013
Simon Hooker
Grape leap forward: New Zealand Winegrowers research and innovation general manager Simon Hooker

Scientists investigating mechanical thinning of grape crops to cut costs and improve profitability stumbled across an unexpected benefit, wine industry representatives learnt at a Grape Days seminar in Blenheim last week.

New Zealand Winegrowers research and innovation general manager Simon Hooker said managing yield was a major focus of the Grape Days programme at the Marlborough Convention Centre in central Blenheim on Wednesday.

Viticulturists were faced with difficult choices when thinning grapes to desired yields, Dr Hooker said. Leave too much fruit on and removing bunches later could be very expensive. Take too much off, and crops could fail to reach projected yields because of cool temperatures or a late frost.

"You can't put fruit back on," he said.

"There's a lot of uncertainty."

Trials had shown mechanical pruning gave growers the option of leaving more sauvignon blanc grapes on the vine, because it was relatively cheap and accurate, Dr Hooker said. Machinery could be dialled up to take off a percentage of the crop.


A panel of 20 tasters confirmed that manipulating yields had no effect on wine quality, he said.

This presumed vines had the ability to ripen the fruit they carried, Dr Hooker said. One vineyard might successfully ripen 15 tonnes of sauvignon per hectare, when others were restricted to 8 or 10t/ha.

Scientists had suspected this mechanical thinning might create conditions that suited botrytis so monitored levels of the disease.

"Weirdly enough, the opposite happened and repeatedly so," Dr Hooker said. "As a result, there was a new tool in the toolbox for sustainable vineyard management."

Scientists involved in a slip-skin project made one of the big breakthroughs of the research year, Dr Hooker said. Plant pathologist Bob Fullerton of Plant & Food Research in Auckland had successfully recreated conditions causing this fungal condition in a laboratory.

"This was a real punt," he said. "There was a fair chance it couldn't be done but the research was successful."

As a result, researchers could work through questions such as whether certain varieties were susceptible to slip skin without leaving the laboratory. There was no need to rush into the field when the problem was reported, often to discover it was done and dusted by the time they arrived.

People attending the Grape Days were especially interested in frost risk and protection, Dr Hooker said.

Winegrowers had not tagged any research dollars to this area but there was enough information out there for growers to be vigilant and proactive rather than reactive, he said.

A three-year study of grapevine trunk disease would be a priority in the next research year, starting next month, Dr Hooker said. Another new project would look into "lifestyle wines" with low alcohol and low calories.

Research focused on five areas; pests and diseases, cost reduction and profitability, organics/sustainability, technology transfer and new wine styles, Dr Hooker said.