`Think before you spray'

BY PENNY WARDLE

Every time you open a chemical bag and tip it into a sprayer, remember your responsibility to the $3.5 billion wine industry.

That was the message from Rex Sunde, who New Zealand Winegrowers employs to prepare spray schedules, when he spoke at last month's Romeo Bragato Conference in Blenheim.

This year NZ Winegrowers' spray schedules feature guidelines towards "nil" chemical residues of less than 0.01 parts per million in wine.

Aiming for chemical-free wines made a good storyline in tough export markets and was a stated aim of NZ Winegrowers, said Mr Sunde. But for a company to pitch itself as residue-free would pit winery against winery and was high-risk if there was a slip-up, he told the Marlborough Express.

A blow for the growers was hearing that the effective botryticide Switch could not be used within 120 days of harvest under the nil residue schedule. The chemical showed up in 20 per cent of samples when it was applied in that period, Mr Sunde said.

Ironically, levels were highest when a particularly good job had been done of targeting bunches, he said.

Red wines were perhaps more susceptible, but residues were still well below legal levels.

Auckland viticulture consultant Tony Hoksbergen suggested that finding out why Switch residues appeared in one in five wines should be a research priority.

More bad news was discouraging results from trials looking at late-season use of "soft" alternative botryticides, including biological controls and sanitisers.

Trevor Lupton, of Gisborne, said Winegrowers trials achieved 75 to 80 per cent control using soft chemicals from flowering to post-bunch closure, but the 10 to 25 per cent of disease that remained nearing harvest was particularly hard to kill.

Possibly, late-season botrytis spread from inside the bunch, rather than from the outside in, he suggested.

"The pressure for residue-free wines will not go away," said Mr Lupton. "We have to learn how to use these products effectively."

Mr Sunde predicted that mandatory residue testing would one day be part of wine export certification, and at $200 per sample, companies should start testing now.

Last year no New Zealand wines tested exceeded maximum residue levels set by the New Zealand Food Safety Authority, he said.

Heavy penalties for exceeding chemical residue limits were a disincentive for failing to comply with market standards, he said.

Mr Sunde was concerned at reports of phosphorous acid being used off-label to control downy mildew in some North Island vineyards.

While registered for use on apples and avocados, the chemical was not approved for grapes, he said.

He was critical that registering a new chemical for use in New Zealand did not require data on efficacy, which Winegrowers considered important.

- The Marlborough Express